Chapter Four
Abnormal Motion during the Gait Cycle For the previously described ideal movement patterns to occur, several factors related to bony alignment, joint mobility and muscular strength must be present. Specifically: 1. Ontogeny should allow for the formation of an aligned lower extremity, particularly in the transverse and frontal planes. 2. The joints of the feet should form a stable medial longitudinal arch that is neither too high nor too low. 3. When the talonavicular joint is maintained in a neutral position and the calcaneocuboid joint is locked in its close-packed position, the plantar metatarsal heads
should all rest on the same transverse plane. 4. The distal extensions of the metatarsal heads should form a smooth parabolic curve. 5. The lower extremities must be of equal length. 6. The articular architecture and ligamentous restraining mechanisms should protect against excessive mobility. 7. The joints of the pelvis and lower extremity should move through certain minimum ranges of motion. 8. Neuromotor coordination must be intact and the supporting muscles must possess adequate strength and endurance.
Figure 4.1. Ideal transverse plane alignment in infants and adults.
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Chapter Four Abnormal Motion During the Gait Cycle genu valgum deformity by externally rotating the tibia, allowing for improved functional alignment at the knee. As with valgus posts in the treatment of tibial varum, the effectiveness of a post is dependent upon the individual’s foot type. This was conclusively demonstrated by Joseph et al. (46), as they measured the ability of varus posts to lessen frontal plane motion at the knee and determined that posts were less effective when used on individuals who pronate excessively. Apparently, flat feet are so efficient at accommodating discrepancies in terrain that they quickly accommodate the post by rolling over it. To get around this dilemma, conservative treatment for valgus deformities at the knee should also include strengthening exercises for the hip abductor, external rotator and adductor musculature, along with gait modifications to reduce toe-out and shorten the individual’s stride length. In severe cases, a Varus Unloader Knee brace should be considered (Fig. 4.19). Development of the Medial Longitudinal Arch The easiest way to categorize foot structure dates back to Galen, when feet were classified simply by the height of the medial longitudinal arch. The longheld belief is that arch height significantly influences foot function: low-arched feet are considered to be hypermobile and prone to pronation related injuries, while high-arched feet are usually described as stiff and prone to high impact injuries. Although injury patterns support the theoretical link between arch height and function (e.g., low-arched individuals frequently present with medial knee and ankle injuries, while high-arched individuals are more likely to suffer stress fractures), early research by Nigg et al. (47) questioned the connection between arch height and 3-dimensional motion. Using calipers to evaluate height of the medial longitudinal arch, these researchers performed 3-dimensional imaging on 30 test subjects and found no correlation between arch height and foot function: individuals with high arches frequently presented with increased calcaneal eversion while low-arched individuals often possessed rigid, less mobile feet. Unfortunately, although their 3-dimensional analysis was extremely detailed, their use of calipers to measure arch height was regrettable, because caliper measurements are easily distorted by hypertrophy of the arch muscles and/or obesity, which significantly alter shape of the arch. Because they may not have accurately identified true arch height, the findings of this study provided little insight into the connection between arch height and motion. In 2001, the controversy regarding arch height and 3-dimensional motion was finally resolved by Williams and McClay (48). Using the highly reliable method of quantifying arch height known as the arch height ratio (described in the next chapter), these researchers performed 3-dimensional motion analysis
Figure 4.19. Anterior view of left leg. The Varus Unloader Knee Brace lessens pressure on the lateral tibiofemoral joint space by pushing (straight arrow) and/or pulling (curved arrows) on the medial and lateral aspects of the knee.
on high and low-arched runners and conclusively demonstrated that arch height and function are indeed correlated: people with low arches have greater rearfoot eversion excursions and velocities, while people with high arches present with increased vertical loading rates. In a follow-up study (57), these same authors determined that arch height was also predictive of injury: low-arched runners exhibited more knee injuries, soft tissue injuries, and medial injuries (e.g., adductor strain, medial knee and ankle injury and sesamoid/first metatarsophalangeal joint injury), while high-arched runners had a greater prevalence of bony injuries (e.g. stress fractures) and lateral injuries (e.g., greater trochanter bursitis, iliotibial band friction syndrome and/or lateral ankle sprains). According to Gould et al. (44), formation of a healthy medial longitudinal arch requires the formation of a well-developed sustentaculum tali, a healthy tibialis posterior tendon, an adequate deltoid ligament, a nonÂconstricted Achilles tendon, and a properly placed 151
Human Locomotion: The Conservative Management of Gait-Related Disorders inferior calcaneonavicular ligament. These authors note that development of the arch is not complete until age 8 and that hyperpronation, often secondary to genu valgum, is the norm for 5 year olds. Though rarely discussed, barefoot activity has been shown to facilitate arch development. In a study of 2,300 children between the ages of 4 and 13 raised in rural India, Rao and Joseph (26) used static footprints to evaluate the influence of footwear on the development of the medial arch. They discovered that children raised without shoes rarely presented with low arches: by age 13, only 2.8% of the barefoot children had flatfeet, compared to an 8.6% prevalence of flatfeet in the children wearing shoes. The prevalence of low arches also varied with the type of shoe gear worn: children wearing closed-toe shoes had lower arches than the children who wore sandals. The authors suggest that because children wearing sandals were more likely to kick them off to play, the resultant interludes of unshod activity may have accounted for the lower prevalence of low arches in this group. The study was interesting as it revealed a clear tendency for arch height to increase with age; e.g., 14.9% of 6 year olds had low arches while only 5.3% of 9 year olds, 3.3% of 11 year olds, and 2.2% of 12 year olds presented with low arches. Because of the higher prevalence of low arches among 6-year-old children wearing shoes compared to those who did not, the authors state that the critical age for development of the arch is before the age of 6. This important research confirms that sensory stimulation associated with barefoot activity may produce a protective increase in muscle tone capable of elevating the arch. This is consistent with research by Robbins and Hanna (50), who confirmed barefoot activity produces measurable increases in adult arch height as seen on weight-bearing X-rays. The protective increase in tone is invaluable in children, as it may permanently alter bony architecture by allowing for the development of a healthy sustentaculum tali. Because obesity increases the potential for developing a flatfoot (51), closely monitoring the development of the medial longitudinal arch in overweight children is imperative, particularly between the ages of 4 and 7. As demonstrated by Gould et al. (44), because the sustentaculum tali is fully ossified by age 7, excessive pronation before that age may mold the sustentaculum tali so that it forms with a downward slope, making it incapable of adequately supporting the talus (Fig. 4.20). Development of the sustentaculum tali is essential for the formation of a functional medial longitudinal arch because it allows the bony architecture to control motion thereby lessening muscular/ligamentous strain during stance phase. Because the typical developmental genu valgum present in 2 to 3 year olds straightens between the ages of 4 and 6 (lessening the medial displacement of body weight responsible for maintaining a low arch), barefoot
Figure 4.20. Posterior view of left calcaneus. In a welldeveloped arch, the sustentaculum tali (ST) forms with an upward angulation (A) that positions the talus directly above the calcaneus. When excessive pronation is present during childhood, the sustentaculum tali often forms with a downward slope (B), which lessens its ability to support the talus.
activity at this time may increase muscle tone allowing for the formation of a healthy arch. In situations where barefoot activity is not possible and/or when the child is significantly overweight, incorporating prefabricated or custom orthotics may be indicated as they may enhance development of the medial arch by lifting the talus off the sustentaculum tali, allowing for normal development of this important bony projection (52). Although not discussed in this text as they are uncommon and often treated with surgical intervention, certain pathological deformities such as the vertical talus, skew foot and/or tarsal coalition may result in the formation of extreme flatfoot deformities. The welltrained practitioner should be able to differentiate these conditions from the nonpathological flatfoot and make the appropriate orthopedic referral. While pathological flatfoot deformities are rarely seen in-office since they are typically treated during the first few months of life, Harris and Beath (53) describe a type of a low arch known as a hypermobile flatfoot that is frequently seen in a clinical setting because it is often symptomatic. In addition to a low arch, this deformity can be identified by the increased range of forefoot inversion (the midtarsal joint may allow for as much as 50째 of forefoot inversion), and rearfoot eversion (the calcaneus is often everted more than 10째 during static stance). Most notably, there is a dramatically reduced range of ankle dorsiflexion (e.g. negative 25째 of ankle dorsiflexion, as measured with the talonavicular joint maintained in a neutral position, is not uncommon). According to Harris and Beath (53) the hypermobile flatfoot results from an inherited malformation in which the sustentaculum tali forms a tongue-like process that projects proximally (Fig. 4.21). The authors note that a superior/inferior x-ray serves 152
Chapter Four Abnormal Motion During the Gait Cycle as a useful index for determining the degree of the deformity as it demonstrates a shadow where the head of the talus is not supported by the anterior calcaneus (e.g., compare the shaded area in Fig. 4.21 to the shaded area in Fig. 4.22). The malformed sustentaculum tali is unable to support the head of the talus and superimposed body weight allows the talus to adduct and plantarflex while the calcaneus simultaneously everts. The excessive talar plantarflexion only serves to amplify the instability, because the head of the talus behaves like a wedge that further separates the incompetent sustentaculum tali from the navicular. Because the plantar ligaments are often unable to contain the head of the talus, the medial arch may collapse completely allowing the talar head to make ground contact. This produces a paradoxical decrease in symptoms as the ground now supports the talus, lessening strain on the plantar talonavicular ligaments (the ground essentially acts as an orthotic). According to Harris and Beath (53), individuals with this deformity often learn to avoid sports and strenuous activities. Although symptoms such as painful joints and/or fatigued muscles may be delayed indefinitely with a sedentary lifestyle, foot pain and discomfort most often begins by the early teens, and may be evident as early as 5 years of age. Whereas the hypermobile flatfoot represents a relatively uncommon genetic cause for the formation of a flattened medial longitudinal arch, reduced arch height may also result from less serious conditions, such as an unstable first ray, a malformed midtarsal joint, a tight Achilles tendon, and any of a variety of other factors (each of these conditions will be reviewed in later sections of this chapter). Regardless of the precise cause, once formed, a low arch can significantly alter motion through the entire kinetic chain. In their 3-dimensional study of runners presenting with high and low arches, Williams et al. (49) confirm that individuals with low arches are more likely to make initial ground contact with a greater degree of rearfoot inversion. A lateral heel contact may represent a learned protective mechanism, because excessive inversion of the calcaneus at touchdown provides tibialis posterior more time to dampen subtalar pronation by allowing the rearfoot to move through a larger range of motion. This may explain why runners who strike on the lateral side of the heel are less likely to be injured (54), and why lifelong runners who have never been injured are more likely to strike the ground with the rearfoot inverted excessively (55). After striking the ground, the calcaneus in lowarched individuals everts 32% faster than in people with high arches (49). The increased eversion velocity may be troublesome as it places greater strain on the restraining muscles and ligaments. In fact, some authors suggest the angular velocity of subtalar joint pronation may play a more important role in development of
Figure 4.21. The poorly developed sustentaculum tali is unable to adequately support the talar head. Adapted from tracings of x-rays as illustrated by Harris RI, Beath T. Hypermobile flatfoot with short tendo Achilles. J Bone Joint Surg. 1948;30A(1):116-138.
Figure 4.22. Ideal development of the sustentaculum tali.
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Figure 4.23. Subtalar stance phase motions with tibial varum and a low medial longitudinal arch. Dotted line represents ideal subtalar motions during stance phase.
various injuries than the overall range of pronation (56). The combination of a low arch and a tibial varum are troublesome because the excessive rearfoot inversion present at heel strike forces the subtalar joint to pronate rapidly through very large ranges of motion. Because subtalar pronation reaches peak angular displacement during the first 50% of the contact period, it is common for the subtalar joint to move through a 16째 range of motion in the first 0.08 seconds of the contact period (Fig. 4.23). The rapid, sometimes extreme range of motion associated with subtalar joint pronation must be dampened by the supporting muscles and ligaments in order for the individual to remain injury-free. A series of potential injuries associated with excessive contact period pronation are illustrated in figure 4.24. In addition to producing various injuries in the medial foot, excessive subtalar pronation may also be responsible for producing injury up the proximal kinetic chain. Tibialis posterior is particularly prone to injury as it has the longest lever for controlling subtalar motion, and is therefore exposed to greater tensile strains. This explains why individuals with hypermobile flatfeet are more likely to develop tibialis posterior tenosynovitis. It is also consistent with prior research showing that excessive subtalar pronation is causally related to medial tibial stress syndrome (58,59). Despite the fact that low arches convert a smaller percentage of frontal plane rearfoot motion into tibial rotation, the transferred rotation is still capable of injuring the tibia, perhaps
because of the increased velocity of calcaneal eversion (49). In a study of 320 cases of stress fractures in athletes, Matheson et al. (60) note a clinical connection between excessive pronation and lower tibial stress fractures. More recently, Milner et al. (61) performed 3-dimensional analysis on runners with and without a prior history of tibial stress fracture and determined the stress fracture group moved through stance phase with greater degrees of rearfoot eversion. It is possible that because the lower tibia has a lower polar moment of inertia (62), it is less able to resist torsional strains associated with excessive pronation, and is therefore more prone to developing stress fractures at that site. While the effect of excessive pronation on the foot and ankle are relatively straightforward, the effect of contact period pronation on knee motion is less obvious. Even though people with low arches move through larger ranges of calcaneal eversion than people with high arches, because they convert a smaller percentage of rearfoot eversion into tibial rotation, the overall range of tibial rotation present during stance phase is about the same in people with high and low arches (49). While clinical research confirms that people with low arches are more likely to develop retropatellar pain (63) and knee osteoarthritis (64), the exact mechanism remains unclear. In an attempt to understand the connection between subtalar pronation and knee pain, LaFortune et al. (65) surgically inserted intracortical rods into 154
Chapter Four Abnormal Motion During the Gait Cycle the proximal tibia, distal femur and central patella of 5 volunteers. Target clusters attached to these rods allowed researchers to measure the exact degree of rotation present between the bones of lower extremity as subjects walked on a treadmill wearing insoles fitted with varus posts (to lessen the degree of pronation) and valgus posts (to increase the range of pronation). When wearing the valgusposted midsole, internal tibial rotation increased 4° more than with the varus midsole. The surprising aspect of this study was that the valgus posts (which increased the range of subtalar pronation) produced no appreciable change in the degree of tibiofemoral joint rotation. This means that as the tibia was forced to internally rotate by the valgus post, the femur rotated the exact same degree so that no net rotation occurred at the tibiofemoral articulation: all of the transverse plane motion induced at the foot by the valgus post traveled through the knee and was absorbed
by the hip. The clinical implication of this research is that excessive pronation is more likely to stress the hip and pelvis than the tibiofemoral joint (Fig. 4.25). The most important finding of the research by LaFortune et al. (65) is that it may explain the connection between excessive pronation and lateral retropatellar pain: they noted the internally rotating femur displaced the lateral femoral condyle into the lateral patellar facet (Fig. 4.26). LaFortune et al. (65) also made the surprising observation that as the foot was forced to pronate by the valgus wedge, the tibia shifted an additional 2 mm medially relative to the femur in the frontal plane. This is significant since the medial shift of the tibia relative to the femur increases tensile strain placed on the anterior cruciate ligament, which could partly explain the clinical connection between excessive foot pronation and an increased prevalence of ACL injuries (66).
Figure 4.24. Potential injuries associated with excessive subtalar pronation. As the subtalar joint pronates, the talus is forced to adduct and plantarflex an excessive amount (A) while the calcaneus simultaneously everts. These actions markedly strain the calcaneonavicular ligament (the sling ligament) and the plantar talonavicular joint capsule. Over time, these exaggerated movements can lead to a pathologic laxity of these tissues. In addition, excessive subtalar pronation may damage the medial band of the plantar fascia, because the talus is displaced anteriorly approximately 1.5 mm with every 10° of calcaneal eversion (B). Manter (313) likens this to the forward motion of a right-handed screw placed directly along the subtalar joint axis: as the calcaneus everts, the screw tightens, thereby pushing the talus anteriorly. While this forward motion is insignificant in an average foot, it may play a critical role in the pathomechanics associated with excessive subtalar joint pronation, as the anterior displacement of the talus causes the navicular and first three rays to move forward and abduct relative to the fourth and fifth rays (C). The forward motion of the medial column irritates the medial plantar fascia, since it places a tensile load on this tissue that may exceed its functional ability to elongate, i.e., the plantar fascia is relatively inelastic. The flexor digitorum brevis may be strained as it attempts to resist forward motion of the medial column by eccentrically contracting. This could result in an increased tractioning of the flexor digitorum brevis muscle’s periosteal attachment, eventually leading to the development of a heel spur (calcaneal spurs form at the attachment of flexor digitorum brevis, not the plantar fascia [76]). The abductory movement of the medial column may also be responsible for injury, because it creates a compressive force at the junction of the medial and lateral column. This may lead to chronic intermetatarsophalangeal bursitis at the third interspace (D).
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Figure 4.25. Placing a valgus post beneath the heel (A) causes an equal increase in tibial and femoral internal rotation (arrows B and C). This increased rotation is decelerated by the hip external rotator musculature (P=piriformis, GS=gemellus superior, OI=obturator internus, GI=gemellus inferior, OE=obturator externus). Prolonged tension in the obturator internus muscle may lead to the formation of a bursa (314) just beneath the ischial spine, where the tendon wraps around the ischium (black dot).
While the individuals in the LaFortune’s study had increased ranges of calcaneal eversion with valgus posts, their findings do not explain the clinical connection between low arches and knee pain, since the typical low-arched person does not present with excessive tibial rotation. Perhaps it is the increased speed of pronation associated with low arches that produces an increased risk for injury. It is also possible that low arches only affect the proximal structures when they occur with other factors that increase lower extremity malalignment; e.g., weakness of the hip external rotators, genu valgum and/or anteverted hips. The combination of low arches and anteverted hips is particularly troublesome since it is almost always associated with excessive valgus collapse at the knee. The resultant valgus collapse may be extreme, particularly when running and jumping. This greatly increases the likelihood of injuring the ACL, MCL and/or the posterior oblique ligament because valgus collapse at the knee increases tensile strain on these important structures (67) (Fig. 4.27). To be comprehensive, conservative treatment should include custom or prefabricated orthotics to lessen the effect foot pronation has on the distal aspect of the kinetic chain, along with specific exercises to control motion at the hip. Because varus wedges are often less effective at reducing valgus collapse when used on people with low arches (46), it is essential that individuals with anteverted hips and flat feet be treated with specific strengthening exercises and agility drills. In a study evaluating the efficacy of these drills in 1,435 Division I college female soccer players, Gilchrist et al. (68) determined that athletes
Figure 4.26. Excessive internal rotation of the femur (A), drives the lateral femoral condyle into the lateral patellar facet (B).
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Figure 4.27. The combination of a low arch (A) and an anteverted hip often results in excessive internal rotation of the entire lower extremity (B), which greatly increases valgus collapse at the knee (C). These actions increase tensile strain on the anterior cruciate ligament (ACL), medial collateral ligament (MCL), and the posterior oblique ligament (POL). The semimembranosus muscle (SM) plays an important role in stabilizing the medial knee. Although a flat foot may increase the degree of valgus collapse at the knee, the combination of excessive foot pronation, valgus knee alignment, and femoral anteversion are collectively referred to as “the miserable malalignment syndrome,� since they significantly increase the potential for valgus collapse at the knee.
1. Warm-up (50 yards each): A. Jog line to line of soccer field (cone to cone) B. Shuttle run (side to side) C. Backward running 2. Stretching (30 secs, 2 reps each): A. Calf stretch B. Quadriceps stretch C. Figure 4 hamstring stretch D. Inner thigh stretch E. Hip flexor stretch 3. Strengthening: A. Walking lunges (20 yards, 2 sets) B. Russian hamstring (3 sets, 10 reps) C. Single-leg heel raises (30 reps on each side) 4. Plyometrics (20 reps each): A. Lateral hops over 2- to 6-inch cones B. Forward/backward hops over 2- to 6-inch cones C. Single-leg hops over 2- to 6-inch cones D. Vertical jumps with headers E. Scissors jump 5. Agilities: A. Shuttle run with forward/backward running (40 yards) B. Diagonal runs (40 yards)
incorporating a series of simple, on-field alternative warmups prior to participating in sport had a 70% reduction in the rate of noncontact ACL injuries. The specific drills used in that study are outlined in Table 1. Because of their proven efficacy, these drills should be recommended for all individuals presenting with even a slight tendency for valgus collapse at the knee, regardless of the cause. Even though excessive pronation associated with a low arch is troublesome during early stance as it overloads the medial foot and is associated with a more rapid rate of calcaneal eversion (49), excessive pronation during late stance is even more likely to result in foot injury as it drives the head of the talus downwardly, forcefully separating the sustentaculum tali from the navicular acetabulum. This action increases tensile strains placed on the plantar calcaneonavicular ligaments (especially the sling ligament) and the plantar fascia, eventually leading to plastic deformity of these important restraining tissues. An overstretched sling ligament is troublesome as the tibialis posterior muscle is unable to compensate for laxity in this important restraining ligament (69) and the talus is allowed to continue its plantar migration, straining the plantar fascia. Over time, the added tensile strains placed on the plantar fascia may inhibit the natural tension banding
Table 1. Preventive exercises/agility drills. As described by Gilchrist (68).
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Human Locomotion: The Conservative Management of Gait-Related Disorders effect associated with windlass mechanism, eventually leading to collapse of the tarsal bones (Fig. 4.28). Biomechanically, the most detrimental aspect of excessive talar adduction is that it increases the body’s lever arm for maintaining the subtalar joint in a fully pronated position throughout midstance and propulsion (Fig. 4.29). This has significant effects on both the proximal kinetic chain and the medial forefoot. During midstance, because the adducted talus is held in a fixed position by superimposed body weight, the external rotational moment created by the swing phase leg is unable to generate a force strong enough to abduct the talus. As a result, the torsional forces associated with this external rotational moment must be temporarily stored in the stance phase lower extremity (Fig. 4.30). The release of these stored torsional forces is occasionally evidenced by a sudden “abductory twist” of the rearfoot the moment the heel lift occurs; i.e., because ground-reactive forces no longer maintain the plantar heel, the entire rearfoot is free to snap medially, as though released from a loaded spring. Because a chain is most likely to give at its weakest link, the prolonged application of these forces may produce transverse plane laxity of the lower extremity joint capsules, and the knee is most likely to be affected by these torsional forces. Coplan (70) corroborated this by noting that individuals possessing excessive ranges of subtalar pronation were more likely to display significantly greater ranges of tibiofemoral rotation, particu larly as the knee approaches full extension (its normal position of function as torsional strains peak during late midstance). In her study, which
Figure 4.28. Normally, the plantar fascia has a tension banding effect (A) that allows imposed forces (B) to induce stability by interlocking the tarsals. Typically, the plantar fascia generates 25% of the force necessary to maintain the arch. This explains why the medial longitudinal arch collapses following surgical release of the plantar fascia. When the tension banding effect of the plantar fascia is absent (C), imposed forces produce a collapse of the tarsals (D) with the dorsal surfaces becoming compressed (E) while the plantar surfaces are distracted (F). Modified from Vogler H. Biomechanics of talipes equinovalgus. J Am Podiatr Med Assoc. 1987;77:21-28.
Figure 4.29. Normally, the talus is positioned almost directly over the calcaneus, thereby supplying body weight with a relatively small lever arm for pronating the subtalar joint (X in A). However, when a high oblique midtarsal joint axis is present (B), abduction of the forefoot occurs with simultaneous adduction of the rearfoot (arrows), which allows for a medial displacement of the talus relative to the calcaneus (arrow m in B and C). This in turn supplies body weight with a more effective lever arm for pronating the subtalar joint (X in C).
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Chapter Four Abnormal Motion During the Gait Cycle was done off weight-bearing, the mean range of tibial rotation when the knee was flexed 5° was 11.4° for the normal group and 18.5° for the pronating group. She speculated that the opposing rotary torques present during the late midstance period produced laxity of the tissues that normally limit knee rotation (although it is also possible that overpronators are more likely to present with ligamentous laxity, which would result in larger ranges of tibiofemoral rotation). Another potential injury associated with these conflicting motions occurs when the anteromedial talar dome collides into the articular surface beneath the medial malleolus (Fig. 4.31). Repeated compression of these two surfaces may eventually lead to chronic synovitis and/or chondromalacia of the talar dome (star). Possibly the most detrimental aspect of excessive subtalar pronation throughout late midstance is that it disallows the normal coupled motions necessary for knee extension; i.e., because the knee is not a pure ginglymus joint, the tibia must externally rotate for the knee to extend smoothly. (The knee can extend without external tibial rotation, but this is a subluxatory rather than a smooth motion.) Excessive subtalar pronation during late midstance presents a biomechanical dilemma in that the tibia is maintained in an internally rotated position as the knee extends. Tiberio (71) mentions that the body might solve this dilemma by means of a process he calls compensatory internal femoral rotation (CIFR). If the femur is able to reverse its usual direction and internally rotate during midstance, normal coupled knee motions would be restored, provided the femur could internally rotate farther than the fixed tibia. The greater range of internal femoral rotation would result in the tibia being in an externally rotated position relative to the femur, thereby restoring coupled motions. Unfortunately, while CIFR solves one biomechanical problem, it creates another when the internally rotating femur drives its lateral femoral condyle into the re spective patellar facet. Tiberio (71) suggested that CIFR, if present, could be an important etiological factor in the development of lateral retropatellar arthralgia. In their 3-dimensional analysis of arch height and motion, Williams et al. (49) note that the femur in low-arched individuals internal rotates farther than the tibia, supporting Tiberio’s concept of CIFR. While excessive subtalar pronation during midstance predisposes to injury because of conflicting movement patterns between the leg and talus, continued subtalar prona tion through the propulsive period may be even more destructive because it maintains a parallelism of the midtarsal axes. The continued parallelism of these axes essentially produces an unlocking of the articulations at a time when maximum
Figure 4.30. When excessive pronation is present, the external rotatory moment created by the swing phase leg (A and B) is unable to generate a force sufficient to shift the subtalar joint from its fully pronated position (C).
Figure 4.31. Conflicting talar and tibial motions during late midstance period. Star represents the point of compression between the anteromedial talar dome and the articular surface beneath the medial malleolus.
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Human Locomotion: The Conservative Management of Gait-Related Disorders (a true Morton’s foot structure is rare). The inappropriate use of a Morton’s extension may result in plantar fasciitis, sesamoiditis and, if continued, may eventually lead to the formation of a dorsal base exostosis (this is often the case when the Morton’s platform is used on an individual with a hypermobile first ray). Because of this, Morton’s extension should only be considered after careful static and dynamic evaluation. A final cause for potential injury occurs when the first metatarsal is the longest metatarsal. It is traditionally suggested that when the first metatarsal is longer than the second metatarsal, ground-reactive forces beneath the first metatarsal head are amplified and the potential for developing hallux limitus/rigidus is greatly increased. While this theory has been supported with some research (149), other studies have found no correlation between an elongated first metatarsal and the development of hallux limitus (150,151). As a result, treatment of the lengthened first metatarsal should only be considered when the individual presents with a symptomatic first metatarsophalangeal joint. That being the case, conservative treatment should include techniques that encourage the individual to maintain a low gear push-off throughout the propulsive period. This may be accomplished by using an orthotic with an extended rearfoot varus post and by having the patient consciously modify his or her gait pattern to maintain a low gear push-off deliberately. Using this approach, the rearfoot is maintained in an inverted position during terminal stance phase, which may allow a moderately lengthened first metatarsal to plantarflex during the propulsive period. Another technique that is useful in treating a lengthened first metatarsal involves fabricating an orthotic with a large rearfoot varus post, then adding a 2-5 long metatarsal post beneath the forefoot. This addition enables the first ray to plantarflex and evert during propulsion, thereby lessening the potential for first metatarsophalangeal joint deformity. If these methods are ineffective and hallux limitus deformity continues to be painful, a rocker bottom should be added to the sole (Fig. 4.83). Unfortunately, Root et al. (79) state that when an elongated first metatarsal has resulted in a hallux limitus deformity, conservative attempts to restore hallux dorsiflexion are useless, and the deformity will continue to progress unless the first metatarsal is surgically shortened. (Although this approach seems a bit extreme, since the habitual use of a low gear push-off coupled with a rocker bottom shoe will alleviate symptoms in the majority of cases.)
develop pain and osteoarthritis on the side of the short limb, while discrepancies of 2 cm or more are associated with pain and osteoarthritis in both knees. Fortunately, most people present with lower extremities of relatively equal length. Although small discrepancies are common, limb length differences greater than 1 cm occur in less than 1 in 1,000 people (162). This contrasts with the upper extremities, where large length differences are common (341). Trivers et al. (341), attribute the smaller length disparities in the lower extremities to natural selection favoring equal limb lengths, since muscular compensation for large LLD is metabolically expensive. Despite the higher prevalence of knee osteoarthritis on the side of the shorter limb, overall, the longer limb is more likely to be injured because it is exposed to greater ground-reactive forces and isometric torque (167). This is consistent with a study by Friberg et al. (153), who evaluated Norwegian military recruits and noted that 73% of stress fractures occurred in the long limb, 16% in the short limb, and 11% of stress fractures occurred in limbs of equal length. The long limb hip is also prone to injury. In a study of 100 patients presenting for total hip replacement, Tallroth et al. (154) determined that 84% had arthritis on the side of the long limb. Although injury is usually associated with discrepancies greater than 1.6 cm, discrepancies as small as 1 cm have been associated with development of low back pain (155,156) and plantar fasciitis (157). Additionally, functional limb length discrepancy secondary to asymmetrical pronation may be an etiological factor in the development of sciatica (158). Because they are treated differently, it is important to differentiate a structural limb length discrepancy (which represents a fixed osseous malformation) from a functional limb length discrepancy (which is most often the result of asymmetrical pronation and/or soft tissue contracture in the pelvis/spine). Unfortunately, differentiating these two deformities is not always easy. In many cases, structural and functional limb length discrepancies occur together, one masking the actual degree of the other (Fig. 4.84).
Limb length Discrepancy Limb length discrepancy (LLD), which is divided into functional and structural categories, is a common cause of injury. In a study of 3,026 subjects with radiographically confirmed LLD, Harvey et al. (152) determined that individuals with 1 cm discrepancies are more likely to
Figure 4.83. A rocker bottom provides a pivot point (I) that allows the foot to move through the propulsive period with minimal bending of the first metatarsophalangeal joint. Although a cobbler can add this addition to most shoes (a 9 mm rocker bottom is a common prescription), it is also possible to buy shoes with rocker bottoms built-in (e.g., Skechers and MBT shoes: see chapter 7).
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Figure 4.84. Masking of limb length discrepancies. A) A functional limb length discrepancy on the left, which is secondary to asymmetrical pronation (B), coupled with a structural limb length discrepancy of the right femur (C), gives the appearance of symmetrical limb lengths. In (D), the rigid plantarflexed first ray on the right (E) produces a functional long limb on that side, which hides the right short femur (F).
To help differentiate structural from functional limb length discrepancy, several examination techniques have been developed. The most accurate of these tests is the scanogram. This technique involves taking a series of x-rays with the central ray initially level with the femoral head, then with the tibial plateau, and finally with the ankle mortise. Information from these x-rays gives exact information regarding the length of the femurs and tibias. An alternate method of x-ray evaluation involves positioning the standing patient with the feet directly beneath the femoral condyles, with the talonavicular joint maintained in a neutral position (which should be maintained muscularly by the patient) and the anterior superior iliac spines (ASISs) equidistant from the buckey. An x-ray taken with the central ray parallel to the femoral heads provides fairly accurate information regarding the relative lengths of the lower extremities (although it is un足able to give exact information regarding lengths of the femurs and tibias). Regardless of which x-ray procedure is used to detect limb length discrepancy, the talonavicular joints should be maintained in their neutral positions, and the femoral neck angles should be measured and compared bilaterally, since these are common causes for functional and structural limb length discrepancies, respec足tively (Fig. 4.85).
Figure 4.85. Asymmetrical femoral neck angles will result in a structural limb length discrepancy.
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Human Locomotion: The Conservative Management of Gait-Related Disorders If exposure to x-ray is a concern or if cost is prohibitive, structural limb length discrepancy may be identified with manual examination techniques. The most common method of evaluation is to position the patient supine and measure the distances from the ASIS to the medial malleolus. Unfortunately, asymmetrical muscle tension may tilt the pelvis, making it difficult to assess discrepancies less than 6 mm. To add to the problem, ASIS to medial malleolus measurements do not take into account the potential for limb length discrepancy arising from structural asymmetries distal to the medial malleolus; e.g., calcaneal fractures and unilateral collapse of the medial longitudinal arch. To be comprehensive, accurate evaluation of limb lengths often requires the examiner combine information from several different manual tests. To begin with, the relative lengths of the femurs and tibiae can be evaluated with Allis’ test (Fig. 4.86). Findings from this evaluation can then be compared to information obtained from a weight-bearing evaluation, in which the levels of the various bony landmarks are observed from front and back (Fig. 4.87). As demonstrated by Hanada et al. (159), placing variable height shims beneath the shorter lower extremity until the iliac crests are level is a moderately valid and highly reliable method for determining the degree of even subtle limb length discrepancy. By combining in formation from the standing evaluation, with information from off weight-bearing and/or x-ray measurements, the practitioner is often able to differentiate structural from functional limb length discrepancy with moderate accuracy. When present, an individual may compensate for a structural limb length discrepancy in a variety of ways. Because the short limb has a longer distance to fall during
late swing phase, many individuals attempt to modify their gait by slowly lowering the shorter limb to the ground via eccentric contraction of the contralateral hip abductor musculature. This frequently results in chronic strain of the gluteus medius muscle and may cause injury to the lumbar spine, since the lumbar vertebrae laterally flex towards the long limb. The effect of limb length discrepancy on spinal motion was demonstrated by Kakushima et al. (160), who noticed the addition of a unilateral 3 cm heel lift increased maximum lateral bending of the lumbar spine from 6.1° to 8.1°. The authors also noted that bending velocities were significantly larger when wearing the heel lift. The authors state the increased range and velocity of lumbar lateral flexion may eventually result in “disabling spinal disorders.” Although these effects were associated with the use of large heel lifts, limb length discrepancies as small as 9 mm have been correlated with the development of degenerative changes in the lumbar spine (162). In an attempt to stabilize against the increased lateral shear forces present at heel strike on the side of the short limb, some individuals develop a toe-out gait pattern prior to making ground contact. Although this protects against excessive lateral displacement of the center of mass, it increases the potential of a fibular stress fracture as toeout gait patterns have been shown to increase the transfer of forces through the fibula (163). This is consistent with Friberg’s study of military recruits demonstrating that although the long limb tibia is more prone to developing stress fracture, the fibula on the side of the short limb was more likely to fracture (153). An alternate pattern of compensation for a short limb occurs when the individual hyperextends the knee
Figure 4.86. Allis’ test. The examiner manually aligns the ASISs so that they rest on the same frontal and transverse plane (A). The medial malleoli are then placed together, and femoral lengths are evaluated from above (B), while tibial lengths are determined by comparing the levels of the tibial plateaus (C).
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Figure 4.87. Weight-bearing evaluation for limb length discrepancies. The patient is carefully positioned with both feet directly beneath the greater trochanters. The level of the medial malleoli (A) can then be compared to determine whether asymmetrical subtalar pronation (or supination) is a cause of functional limb length discrepancy. Next, the tibial plateaus are compared (B) to determine the relative lengths of the tibiae. To compare femoral lengths, the fingertips are placed on top of the greater trochanters (which can be found by having the patient flex and extend the hips), and their respective levels are noted (C). Finally, the levels of the posterior superior iliac spine (PSISs) and iliac crests should be compared (D), and any deviation of the lumbar spine from vertical should be noted (E).
and inverts the rearfoot on that side. While both of these motions may be helpful in bringing the heel closer to the ground during late swing phase, they may be damaging in that hyperextension of the knee impairs the quadriceps ability to dampen vertical forces, possibly explaining the higher prevalence of tibiofemoral osteoarthritis on the side of the short limb (152). The sacroiliac joint is also prone to injury on the side of the short limb as, in an attempt to level the pelvis, the innominate tilts anteriorly (164) (Fig. 4.88). Because of the limited range of motion available to this joint, the compensatory obliquity (which occurs as the pelvis twists between 2째 and 6째 [165]) greatly stresses the sacroiliac joint, possibly impairing its ability to absorb shock through sacral nutation because the ilium is maintained in an end-range position. This may explain why the sacroiliac joint on the side of the short limb shows earlier and more extensive degenerative changes than the sacroiliac joint on the side of the long limb (166). On the side of the longer lower extremity, in addition to increasing the potential for tibial stress fractures and osteoarthritis of the hip, compensation for a long limb may also produce injury at the foot and/or ankle. Because the long limb is subjected to greater pressure beneath the hallux, and the propulsive period on the side of the long limb occurs with a more rapid heel lift (167), the potential for injuring the first metatarsophalangeal joint and/or the
Figure 4.88. Pelvic compensation for a limb length deficiency. To keep the spine vertical, the innominate on the side of the short limb (A) tilts anteriorly (B), while the innominate on the side of the long limb tilts posteriorly (C).
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Human Locomotion: The Conservative Management of Gait-Related Disorders Achilles tendon greatly increases. Furthermore, because the long limb moves through a larger arc during swing phase (168), the individual often attempts to decrease the radius of this arc by flexing the knee, which may increase the potential for retropatellar injury during the contact period. While increasing the degree of knee flexion is the most effective way to compensate for a longer limb, it is also possible to bring the longer limb closer to the ground by maximally pronating the subtalar joint on that side. Even though Sanner et al. (169) note an average vertical change of only 3 mm as the subtalar joint moves from a neutral position to a pronated position, it is possible for subtalar joint pronation to compensate for structural limb length discrepancies of 12 mm or more. In some cases, the head of the talus will actually make ground contact. Ironically, Hiss (170) claims that this makes the foot more stable, because plantar contact with the talar head serves as a point of support for the unstable medial column. As a result, even though it is a commonly held belief that the greater range of subtalar joint pronation occurs on the side of the structurally short limb, it is possible that an even greater range will occur on the side of the long limb if the individual attempts to level the pelvis. Treatment in this situation requires placing a lift beneath the short limb and, if the range of subtalar joint pronation on the long limb side remains unchanged, an orthotic may be necessary to control the exaggerated motion. Novick and Kelley (171) note that the addition of a 2 mm thick functional orthotic produces a 4.8 mm elevation of the ankle joint’s center of mass secondary to superior repositioning of the talus on the calcaneus. Because of this, treatment for combinations of structural and functional discrepancies requires careful pre- and post-evaluation to ensure that proper correction has been attained. If a structural limb length discrepancy were present by itself, treatment should consist of placing the appropriately sized lift beneath the short limb. The actual height of the lift is best determined by placing lifts of various sizes beneath the short limb and reevaluating alignment. The ideal lift will level the iliac crest and, more importantly, bring the lumbar spine to vertical (148). This technique is surprisingly accurate for even subtle limb length discrepancies. If a heel lift is recommended based upon information from off weightbearing measurements (e.g., ASIS to medial malleolus), it is necessary to add approximately 33% to the measured discrepancy in order to attain full correction; i.e., because the talus is positioned one third of the way between the calcaneus and metatarsal heads, a heel lift placed beneath the calcaneus will raise the talus only two thirds of that distance. For example, a 6 mm lift will raise the talus 4 mm. Because they may adversely alter motion and/or transfer weight to the medial forefoot, when possible, fulllength insole lifts are preferred over heel lifts.
Most authorities recommend that lifts be used for structural limb length discrepancies greater than 6 mm (172,173). However, Subotnick (174) claims that because of the 3-fold increase in ground-reactive forces associated with running, heel lifts should be used on running athletes that present with structural limb length discrepancies greater than 4 mm. Travell and Simons (148) are less concerned about the effects of relatively small limb length discrepancies. They recommended a 7 mm structural limb length discrepancy be treated only when it is suspected of being a perpetuating factor in myofascial pain syndromes. Otherwise, it is suggested that heel lifts be used preventively only in the treatment of structural limb length discrepancies exceeding 12 mm or more. As demonstrated by Song et al. (175), even this degree of limb length discrepancy need not be treated with a lift, since these authors demonstrate that limb length discrepancies less than 3% of the length of the longer extremity (approximately 2.25 cm) are not associated with compensatory movement strategies. (Although these numbers seem a bit extreme since discrepancies greater than 6 mm are readily observed during gait analysis as the long limb hip elevates excessively during midstance while walking, see Fig. 4.89). Because of conflicting research regarding the degree of discrepancy necessary to justify treatment, the use of a lift should be based upon physical examination (i.e., is a compensatory gait pattern visible) and the patient’s symptoms; e.g., strain of the right gluteus medius muscle responds well to a left heel lift, while right sacroiliac pain responds well to a right heel lift. When a limb length discrepancy is clear upon gait evaluation and the location of the symptoms match with the side of the discrepancy, it is suggested that limb length differences greater than 6 mm be treated with the appropriately sized lift. When the limb length discrepancy is associated with compensatory pelvic obliquity and/or asymmetrical muscle tension, manipulation, deep tissue massage and specific home mobilizations are usually necessary to restore mobility and improve muscle function.
Figure 4.89. Even a slight limb length discrepancy produces visible changes during gait analysis as the center of mass (dots) moves with an alternating sine wave pattern, reaching a peak during midstance on the side of the longer limb (A), and dropping as it travels over the shorter limb (B).
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Chapter Four Abnormal Motion During the Gait Cycle Interestingly, it is often the case that incorporating a heel lift to compensate for structural limb length discrepancies in children under the age of 15 results in the complete disappearance of the limb length discrepancy (i.e., limb lengths become equal) after 3-7 months of wear (176). As a result, children should be evaluated at 6-month intervals to determine whether the heel lift is still necessary. Because of problems with shoe fit, it is recommended that heel lifts greater than 9 mm be added to the midsole or heel and not placed inside the shoe. Heel lifts that run the full length of the midsole will prevent contracture and reduce atrophy of the posterior calf musculature, a common problem when elevating the heel alone. Additionally, to reduce the risk of injury to the contralateral hip flexors and adductors (which are stretched with heel lift), large structural limb length discrepancies should be treated by gradually increasing the size of the heel lift at a rate of approximately 6 mm every 4 weeks. During this break-in period, the rectus femoris, iliopsoas and adductor musculature should be gently stretched to reduce the potential for iatrogenic injury. A primary contraindication for heel lift therapy occurs when the lumbar spine is not laterally flexed toward the structurally short leg. Use of a heel lift in this situation could result in recurrent injury to the lumbosacral spine. Another contraindication is that a heel lift should never be used to treat a functional limb length discrepancy because the lift does not address the cause of the discrepancy and may even create a unilateral weakness of the involved lower extremity (177). Treatment for a functional limb length discrepancy requires the appropriate manual therapies to address the soft tissue contractures that may be twisting the pelvis and, if necessary, an orthotic to correct asymmetrical pronation that may be causing the limb length discrepancy. In a study in which a combination of custom orthotics and manipulative techniques were used to correct functional limb length discrepancies secondary to asymmetrical pronation and its associated sacroiliac joint dysfunction, Rothbart and Estabrook (158) noted that 78 of the 81 patients treated exhibited a complete reduction in low back pain with 77% of these individuals remaining asymptomatic 6 months after their last manipulative treatment. The authors related the reduced chronicity to the fact that the orthotics maintained a more functionally efficient posture, thereby allowing even short-term manipulation (i.e., 3 weeks) to have a more permanent effect. Isolating the exact degree of structural vs. functional limb length discrepancy is not always easy and requires careful observation and examination. Before casually recommending a heel lift based upon information obtained from a single ASIS to medial malleolus measurement, the practitioner should have fully evaluated respective tibial and femoral lengths in a variety of positions, checked for soft tissue contracture that might be twisting the pelvis, and carefully evaluated foot function to determine whether
asymmetrical subtalar joint motion is contributing to a functional limb length discrepancy. Prior to prescribing a heel lift, a simple test can be performed during physical examination that is surprisingly helpful for confirming the weight-bearing and off weight-bearing measurements. By having the upright patient shift body weight back and forth between the right and left leg, and asking them to stand on the more comfortable lower extremity, the vast majority of patients will stand on the shorter lower limb, as this levels the lumbar spine and reduces pressure on the chronically overworked long limb hip abductor musculature. If the patient consistently finds it more comfortable to stand on what you have measured to be the longer lower extremity, the decision to incorporate a heel lift should be reconsidered. Excessive Mobility Because ground-reactive forces present during locomotion can be extreme, the most reliable protection against injury is a well-designed skeletal system. Ideally, the various articulations of the lower extremity will form in such a way that the superimposed stresses of weightbearing allow the joints to interlock with ligamentous restraining mechanisms that enhance stability. The classic example of this is the sacroiliac joint, where sacral nutation during the contact period is resisted by tension within the sacrotuberous ligament. This not only lessens the potential for injury, it also improves metabolic efficiency, because ligaments, unlike muscles, do not consume calories. There are, however, numerous congenital anomalies that significantly impair the ability of bony/ligamentous restraining mechanisms to resist excessive motion. The joints most likely to be affected are listed as follows: The tibiofemoral joint: While the depth of the ball and socket hip joint provides inherent stability that reduces stress on the restraining ligaments, the tibiofemoral joint is not as fortunate, since the flat tibial plateau provides little protection against excessive motion. This is particularly true when the knee approaches full extension, as the femoral condyles roll forward with little restraint. To protect against hyperextension, most people possess a slight posterior slope of the tibial plateau that increases pressure centered beneath the anterior femoral condyles thereby creating a slight flexion moment that limits hyperextension. Unfortunately, posterior sloping is not always present and the individual with a horizontal tibial plateau is more dependent upon soft tissue restraining mechanisms (Fig. 4.90). While most authorities claim that a hyperextended knee (also known as genu recurvatum) results from laxity in the cruciate ligaments, collateral ligaments and/or posterior capsule, Morgan et al. (178) prove the posterior oblique ligament provides the most powerful restraint to hyperextension. In a cadaveric study in which ligaments were sectioned one at a time and the resultant degree of hyperextension noted, these authors demonstrate that 189
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Figure 4.116. Popliteus length test. Tension in popliteus is evaluated by abducting the forefoot (arrow) while the knee is flexed 30째. Tightness may cause the individual to walk with the knee slightly flexed at heel strike. Sitting with the hip in a Faber position with the leg tucked under the opposite thigh promotes contracture.
Figure 4.118. Semimembranosus and semitendinosus length tests. These muscles are tested by performing a straight leg raise with the lower extremity externally rotated while slightly abducting the hip. Tightness in these muscles will produce a slight toe-in gait pattern. As with contracture in the bicep femoris, individuals with contracture in the inner hamstrings significantly shorten their stride length and occasionally switch to a forefoot strike pattern to lessen strain on the hamstrings during late swing phase.
Figure 4.117. Bicep femoris length test. Performing a straight leg raise with the lower extremity internally rotated and slightly adducted stretches the bicep femoris. Contracture in this muscle is a common cause of a toe-out gait pattern, particularly in runners. In addition, tightness in the bicep femoris reduces the length of stride, and the individual often switches to a lateral forefoot strike pattern. Tightness is perpetuated by sleeping in a fetal position and by sitting in chairs in which the distal aspect of the chair curves upwardly, compressing the short head of the bicep femoris.
Figure 4.119. Posterior gluteus medius length test. The posterior fibers of gluteus medius are assessed by adducting the slightly flexed hip and comparing ranges bilaterally. Tightness in this muscle produces a slight toeout gait pattern with a slightly wider base of gait. Trigger points in the gluteus medius muscle frequently refer pain to the lateral leg, mimicking L5 radiculopathy.
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Figure 4.121. Adductor length tests (long adductors). By slightly flexing the hip and externally rotating lower extremity, tension in adductor magnus and gracilis can be evaluated by slowly abducting the involved hip (arrow). When the hip is fully abducted, tension in the pectineus, adductor longus, and adductor brevis muscles may be evaluated by slowly pushing involved ankle towards the floor. Tightness in these muscles may be associated with a crossover gait pattern and reduced stride lengths. Contracture is perpetuated by sidelying sleeping positions and adductor weakness.
Figure 4.120. Anterior gluteus medius and tensor fasciae latae length test. By flexing the contralateral hip and knee (A), involved hip may be adducted (B) thereby stressing the central and anterior portions of the gluteus medius muscle. By extending the involved hip slightly off the table, tension in the gluteus minimus and tensor fasciae latae may be identified. Excessive tightness in gluteus minimus and tensor fasciae latae may internally rotate the involved lower extremity during late stance and early swing phase. In addition to causing an iliotibial band friction syndrome, tightness in these muscles may also cause a greater trochanteric bursitis. An effective method for lengthening these muscles involves having the examiner stabilize the pelvis and contralateral leg while adducting the involved lower extremity with a flexed knee (C). With practice, this technique allows the practitioner to very accurately identify and treat tightness in specific areas of the anterior gluteus medius, gluteus minimus and tensor fasciae latae musculature. These stretches are especially effective when performed following deep tissue massage of the affected muscle groups.
Figure 4.122. Adductor length tests (short adductors). By placing the patient in a figure 4 position, the examiner stabilizes the contralateral pelvis while pushing down on the involved knee. This position identifies tightness in the adductor longus, brevis, and pectineus musculature. Tension in the ischiocondylar portion of the adductor magnus muscle can be evaluated by moving the foot proximally up the contralateral thigh (arrow A) and then pushing downwardly on the involved knee (curved arrow). Tightness in these muscles frequently produces a crossover gait pattern with shortened stride lengths and limited hip extension during the propulsive period. Contracture is perpetuated by sleeping with the hip flexed and adducted in a sidelying position.
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Figure 4.123. Piriformis length test. Tension in the piriformis muscle is tested with the involved hip flexed 35° while the examiner pulls the ipsilateral knee medially. In addition to irritating the static nerve, contracture in the piriformis muscle is a common cause for toe-out gait patterns. Tightness is perpetuated by sleeping prone or supine in a figure 4 position, which frequently occurs in patients with retroverted hips.
Figure 4.124. Obturator internus and externus length test. With the involved hip flexed 90°, the examiner pushes the patient’s knee medially into horizontal flexion. An alternate method to test tension in the obturator muscle is to place the knee of the patient’s flexed hip against the examiners chest and then push the patient’s vertical thigh downwardly. By slightly altering the degree of hip flexion and horizontal flexion, different aspects of the hip external rotator musculature can be assessed. As with the piriformis muscle, tension in these muscles frequently results in a toeout gait pattern and may be perpetuated by figure 4 sleeping positions. Contracture in any of the hip external rotators may alter the hip’s axis of motion during horizontal flexion, producing anterior acetabular impingement syndrome, or even anterior labral injury.
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Figure 4.125. Quadriceps muscle length test. Tension in the vastus lateralis muscle is tested by fully flexing the patient’s hip and knee. Tension in the vastus intermedius muscle is tested with the hip straight and the knee fully flexed (the patient is positioned on the edge of the examining table so the knee can be flexed off the side of the table). Travell and Simons (320) suggest testing length in the vastus medialis obliquus muscle by placing the patient in a Faber position (as in figure 4.122) and maximally flexing the knee by pushing the ankle upwardly, toward the pubic symphysis. Quadriceps tightness is a common cause for chronic retropatellar pain.
Figure 4.127. Prone hip flexor length test. By stabilizing the low back to prevent hyperextension of the lumbar spine, the examiner extends the hip and notes the distance the lower extremity can be extended bilaterally. This position also serves as an excellent test for evaluating contracture in the tensor fasciae latae muscle by adducting the extended hip.
Figure 4.128. Rectus femoris length test. While stabilizing the lumbar spine, the examiner flexes the involved knee and measures the heel to buttocks distance bilaterally (arrow). Because the rectus femoris muscle crosses the hip joint, contracture in this muscle produces hyperextension of the pelvis and lumbar spine as the knee is flexed. This is readily palpated with the stabilizing hand and the length test should be stopped once spinal motion is noted. Tightness in this muscle is a frequent cause of retropatellar pain syndromes (including plical band syndromes) and the contracture is occasionally perpetuated by sitting for long periods with the knees extended (i.e., the long-sitting position). By performing deep tissue massage over specific areas of the muscle and repeating the length test, the precise section of the muscle responsible for limiting motion may be identified. The upper portion of the rectus just distal to the tendon is notorious for limiting motion.
Figure 4.126. Thomas test for hip flexor contracture. By having the supine patient actively bring their knee towards their abdomen, the contralateral thigh should remain flat on the table. When contracture of the hip flexors is present, the uninvolved thigh lifts off the table (arrow). During the gait cycle, iliopsoas contracture may result in excessive spinal flexion during late stance, a shortened stride length from deceased propulsive period hip extension, and may even result in chronic hip pain from impaired circulation to the femoral head and pinching of the anterior labrum (see figure 4.101). Hip flexor contracture is perpetuated by sleeping in the fetal position and sitting in chairs with the knees higher than the hips.
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Figure 4.129. Quadratus lumborum length test. The standing patient is asked to flex the spine slightly and laterally flex in each direction. Length of the quadratus lumborum muscle is compared by noting the distance the hand contralateral to the side being tested moves down the thigh. These distances are compared bilaterally. This test is also useful when evaluating limb length discrepancy, as the hand can move farther down the shorter lower extremity.
Figure 4.130. Gastrocnemius and soleus stretches. Gastrocnemius is stretched with the hip and knee extended while the soleus muscle is stretched in the same position with the knee flexed (arrow). The medial fibers of the gastrocnemius muscle may be accessed by having the patient internally rotate the lower extremity while performing this stretch. This stretch may also be performed by standing on a slant board.
Figure 4.131. Tibialis posterior and medial soleus stretch. With the leg internally rotated and the knee slightly flexed, tibialis posterior and the medial soleus muscles are very effectively stretched. The long digital flexors may also be stretched in this position by placing a rolled up towel beneath the toes.
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Figure 4.181. Knee mobilizations/manipulations. The tibiofemoral joint is mobilized with gentle gliding/rotational movements performed at the end-ranges of flexion and extension. Prior to performing mobilizations, the knee is loosened with a muscle energy stretching pattern in which the knee is extended while the leg is externally rotated (A), and flexed when the leg is internally rotated (B). After moving the knee through progressively larger ranges, the knee is fully flexed and posterior glide of the tibia may be restored by applying a gentle thrust to the proximal tibia (C). This manipulation is performed while internally rotating the tibia by applying greater pressure on the medial side of the knee. Although not illustrated, extension of the knee is restored by fully straightening the tibiofemoral joint and applying downward pressure on the distal femur while the heel is supported by the table. This mobilization should be performed at home for up to 30 minutes daily by having the supine or seated patient place his/her heel on an elevated surface with 2 to 5 pound weights positioned over the distal femur of the straightened lower extremity. This is a popular method for restoring motion following knee replacement.
Figure 4.182. Long axis manipulation of the hip joint. With the involved hip flexed slightly, the examiner tractions the lower extremity and applies a gentle long axis manipulation once the elastic barrier is felt. In a study of 109 patients with hip arthritis, this manipulation, when performed after a series of gentle stretches, produced greater improvements in pain, function and range of motion than a standard exercise program. After 5 weeks of treatment, 81% of the manipulation group improved, compared to only 50% of the individuals treated with a conventional exercise routine (325).
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Figure 4.183. Long axis compression with the hip flexed. The involved knee of the patient’s flexed hip is tucked along the medial border of the examiner’s deltoid muscle and a long axis compressive forces generated along a line paralleling patient’s femur (arrow). The examiner varies the degree of flexion, evaluating muscular resistance to long axis compression at each angle. When resistance is noted, the examiner uses the left hand as an anchor to create a powerful compressive force through the shoulder and left upper extremity. Before performing this mobilization, the patient usually performs a series of mild muscle contractions to relax the involved muscles. Besides stretching the hip external rotators and posterior capsule, this maneuver serves as an excellent method to test the stability of the sacroiliac joints, which, when inflamed, produce localized pain when the hip is compressed.
Figure 4.185. Extension manipulation of the right sacroiliac joint. This manipulation is useful for treating a functionally short limb. With one hand over the PSIS (pisiform contact) and the other forearm stabilizing the lower extremity just above the knee, the patient’s hip is extended until the right sacroiliac joint reaches its elastic barrier. At that point, a light thrust is applied to the right PSIS. This position can also be used to perform muscle energy stretches on the tensor fasciae latae, iliopsoas and gluteus minimus muscles by adducting the involved hip.
Figure 4.186. Extension mobilization of the lumbar spine. This mobilization is performed by placing closed fists along one side of the lumbar spine (usually directly over the erector spinae musculature) and applying a straight downward mobilization with the right and then left hand. The action is performed with a rocking motion between the hands. To relax the psoas muscle, the examiner temporarily maintains the hands in a fixed position and asks the patient to flex the hip by pulling the knee into the table (i.e., “gently pull your right knee into the table”). This is followed by continued extension mobilization of the lumbar spine.
Figure 4.184. Inferior glide mobilization of the hip joint. Applying inferior glide to the proximal femur increases the range of hip flexion. This manipulation can be performed after a series of muscle energy stretches on the gluteus maximus muscle.
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Figure 4.189. Lateral flexion manipulation of the lumbar spine. This manipulation is applied with the same setup as the rotational lumbar manipulation, only the downside innominate is pulled inferiorly during the setup, laterally flexing the lumbar spine in the desired direction. The manipulation is applied with a slightly downward force (arrow). Modified from Peterson and Bergman (326).
Figure 4.187. Flexion manipulation of the left sacroiliac joint. The examiner places the patient in a sidelying position and has the patient cross hands just below the chest. With a pisiform contact beneath the lower posterior inferior iliac spine (A), the examiner applies a high velocity, low amplitude thrust through the lower aspect of the sacroiliac joint (arrow). The patient’s torso is stabilized as the examiner’s upper hand is placed over the patient’s hands. Before performing the manipulation, the pelvis and shoulders are preset by pulling the lower innominate and upper extremity downward and forward. Modified from Peterson and Bergman (326).
Figure 4.188. Rotational manipulation of the lumbar spine. With the patient in a sidelying position, the vertical pelvis is rotated towards the examiner, while the patient’s torso is held in a stable position with the examiner’s opposite hand. The examiner then uses his or her own knee to flex the patient’s knee until the specific joint to be adjusted is felt to open. Using a pisiform contact (dot), a dynamic thrust is applied directly through the desired lumbar joint (arrow). Modified from Peterson and Bergman (326).
Figure 4.190. Home lumbar lateral flexion mobilization. The patient rests in a comfortable position with the hips and knees flexed. To mobilize the lumbar spine in lateral flexion, the patient alternately shifts the innominates up and down in the frontal plane (arrows). This is performed for approximately 1 minute, 3 times per day and may be performed prone to restore extension and lateral flexion.
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Figure 4.191. Muscle energy mobilization of the sacroiliac joints. Before mobilizing the sacroiliac joint with home flexion/extension stretches, the patient alternates between pushing in and out at the knees. This is performed for approximately 1 minute.
Figure 4.192. Flexion mobilization of the right sacroiliac joint. The standing patient places the foot of the involved lower extremity on a stool, maximally flexing the hip and involved sacroiliac joint. A hold-relax stretch may be performed in this position, in which the knee is gently pushed into resistance provided by the crossed arms. This position is held for 35 seconds and repeated 5-10 times per day.
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Figure 4.193. Alternate flexion mobilization of the right sacroiliac joint. The sacroiliac joint may also be mobilized by placing the foot of the involved lower extremity as high as possible against a door jam. By gently pressing against the door jam and then moving the foot slightly superiorly, the sacroiliac joint on that side is mobilized in flexion.
Figure 4.194. Extension mobilization of the right sacroiliac joint. By placing the knee on the edge of a table, the right ilium is mobilized in extension as the hip is extended (arrow). Note the patient’s torso is maintained in a vertical position. This mobilization is usually performed after repeating a series of hold-relax stretches on the right hip flexors; i.e., the knee is gently pressed into the table as the individual relaxes and moves slightly forward, thereby increasing the range of hip extension.
Figure 4.195. Alternate extension mobilization of the left sacroiliac joint. This home mobilization is performed with the relaxed patient allowing the involved hip to extend off a table or bench. This is usually performed for 60 seconds and repeated 5 to 10 times per day.
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Chapter Four Abnormal Motion During the Gait Cycle Neuromotor Coordination and Strength This is one of the more important criteria for normal function since the strong, well-coordinated individual is often able to manage even large structural malformations without injury, while a weak, uncoordinated person may be constantly injured as he or she responds to even minor changes in terrain with uncontrolled, inappropriate movement patterns. To move in a coordinated and efficient manner, the body must analyze thousands of signals from a wide range of sensory organs that constantly barrage the somatosensory and parietal cortices of the brain with information regarding muscle length changes, tendon tension, weight distribution, temperature and pressure. Even the effect a strong gust of wind might have on locomotion can be calculated by evaluating information from the small movements of hair follicles. Signals from these diverse receptors are evaluated and an appropriate motor response is immediately initiated. Sherrington refers to the information derived from the small, densely packed sensory receptors located in our muscles, tendons and skin as our sixth sense: the sense of proprioception. Derived from the Latin proprius, for perception of one’s own, proprioception is underappreciated as a sense and it is fundamental not just for locomotion, but also for survival. While loss of any other sense, even vision, can be compensated for by sharpening the remaining senses, loss of proprioception can have disastrous consequences. This is demonstrated by Ian Waterman, who had the misfortune of developing a rare neurological condition in which the sensory fibers carrying proprioceptive information from the neck down were destroyed, while motor nerves were spared. As described by Smetacek and Mechsner (263), Ian was unable to sense his body’s position in space and whether or not he was moving. By age 19, he was unable to stand and had to be fed, washed, and dressed by others, and any attempt to produce movement resulted in uncontrolled flailing of the extremities. Over time, Ian learned he could control certain movements with his eyes, teaching his motor cortex to associate a given motion with the corresponding visual feedback. Controlling motion through visual cues was not an easy task. Even after 30 years of constant practice, Ian claimed the concentrated focus on visual attention necessary to make the simplest movements was comparable to running a daily marathon, and after all this time, he would collapse like a rag doll when it became dark. The authors emphasize that Ian’s case history, and a few others like it, confirm “all purposeful movements, both conscious and unconscious, are controlled by proprioception.” The proprioceptive input so important for survival originates from sensory organs know as mechanoreceptors, which are located in the muscles, tendons, joint capsules, and other associated deep tissues. These sensory organs are categorized into 3 different groups depending upon their location: muscle mechanoreceptors, mechanoreceptors
of the joints and skin, and labyrinthine and neck mechanoreceptors. As a group, mechanoreceptors relay constant information regarding static and dynamic joint positions; i.e., some of these receptors are slow to adapt and discharge only when the joint is held at a specific angle, while others are rapidly adapting and discharge in bursts to signal changes in acceleration or tension. The muscle mechanoreceptors consist of the muscle spindle and the Golgi tendon organs (GTOs). Spindles, which are considered the most important receptors for kinesthetic awareness (264), are located in parallel series within contractile muscle fibers and consist of fluid-filled capsules 2 to 20 mm long, enclosing 5-12 small specialized muscle fibers referred to as nuclear chain and nuclear bag fibers. Collectively, they are referred to as intrafusal fibers (Fig. 4.196). The nuclear bag fibers are very sensitive to stretch and, via primary afferents, relay information regarding dynamic changes in muscle length, i.e., phasic responses. Conversely, the nuclear chain, which is innervated by both annulospiral and flower spray nerve endings, relays information regarding the static position of muscle fibers, i.e., tonic responses. The sensitivity in which these receptors will discharge can be preset by activating the gammamotor neurons: by producing contraction at the polar ends of the intrafusal fibers, the gamma-motor neurons increase tension on the central portions of the chain and bag (particularly the bag), producing a heightened sensitivity to a change in length (Fig. 4.197). The process of setting spindle sensitiv ity via gamma-motor neuron activity is referred to as gamma-bias. The gamma-motor neurons may also produce voluntary movement via an indirect pathway known as the gamma-loop. In this pathway, signals from the pyramidal tract, which in a more direct pathway would travel directly to the alpha-motor neurons to produce movement, activate the gamma-motor neurons to tense polar portions of intrafusal fibers to the point of stimulating their afferents. This in turn sends a signal back to the cord, which traverses a monosynaptic pathway to activate the appropriate alphamotor neuron. Although this obviously occurs at a much slower rate, stim ulation of the gamma-loop system is associated with a greater control of muscular actions. In most situations, voluntary movements are accomplished by a combination of direct and indirect (via gamma-loop) activation of the alpha motor neurons referred to as alphagamma coactivation. While activation of spindle afferents will result in reflex contraction of the neighboring muscle fibers, activation of the Golgi tendon organs (which are located in the tendon fibers near the muscle tendon junctions) will produce autogenic inhibition or relaxation of the involved muscle. Because muscles are capable of producing greater contractile forces than their own structural makeup can withstand, the Golgi tendon organs play a protective role 237
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Figure 4.196. The intrafusal fiber and its innervation. Modified from Netter F. The Nervous System. Part 1, Anatomy and Physiology. West Caldwell, NJ: The CIBA Collection of Medical Illustrations, 1985.
by inhibiting contraction (and facilitating the antagonist), should the contractile force become too great. Although these receptors have relatively low thresholds (i.e., the GTOs located in a cat’s soleus muscle will discharge with an applied force of less than 0.1 g [265]), their inhibitory effect may be offset by the annulospiral activity associated with voluntary movement. In fact, success with strength training depends upon the ability of the athlete to learn how to inhibit information from Golgi tendon organs successfully. In a study delineating interactions between annulospiral and GTO fibers, Hufschmidt (266) found that a stimulus sufficient to excite both the annulospiral and Golgi tendon organs produces only facilitation, indicating the inhibiting effect of the Golgi tendon organ can somehow be canceled. Apparently, the GTOs supply the spinal cord with constant feedback regarding the forces acting on the muscle and produce inhibition only when danger ously high-tension levels are reached. Unlike the muscle mechanoreceptors (GTOs and spindles), information from joint and skin mechanoreceptors travel all the way to the cortex and, because their receptors connect with so many interneurons, they are able to modify
Figure 4.197. Stimulation of the gamma motor neurons produces contraction at the polar ends of the intrafusal fibers (arrows), which creates a heightened sensitivity in these fibers, as the nuclear region is now tensed. Modified from Gowitzke BA, Milner M. Scientific Bases of Human Movement. Ed 3. Baltimore: Williams and Wilkins, 1988.
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Chapter Four Abnormal Motion During the Gait Cycle activity favorably in all limbs, not just the stimulated limb. In addition, joint and skin receptors also have a facilitatory effect upon the vestibular apparatus which, by enhancing activity in specific motor neurons, acts to stabilize the extremities dur ing the gait cycle by stimulating the requisite muscles to contract with more force. When properly functioning, the various joint, skin, and muscle proprioceptors work together to supply the cen tral nervous system with a constant barrage of diverse sensory information regarding body position and movements. In ways that are still poorly understood, the central nervous system analyzes this information by comparing it to a desired pat tern (which nature, conditioning, and experience have established) and produces the most appropriate motor response. The cycle is then immediately repeated, wherein each response is analyzed and the movements are fine-tuned. A perfect example of how proprioceptors and muscles interact to produce a desired action occurs during the positive supporting reaction. In this reflex, groundreactive forces present during early stance phase spread the metatarsophalangeal joints, stretching the interossei muscles. Information from the stimulated muscle and joint mechanoreceptors triggers a reflex contraction of the extensor musculature, particularly the quadriceps. This reflex contraction stabilizes the weight-bearing extremity by controlling knee flexion with just the right amount of muscular tension: too much tension would interfere with shock absorption while too little would cause the knee to give way. The importance of the foot proprioceptors is clear to anyone who has ever had his or her foot fall asleep after sitting cross-legged: upon standing, the knee may buckle slightly as the temporary anesthesia associated with circulatory impairment inhibits the positive supporting reaction. O’Connell and Gardner (267) verified the significance of the foot proprioceptors by performing an experiment in which a blindfolded individual was suddenly dropped from an elevated chair onto a gymnasium floor mat. (By randomly raising and lowering the chair various amounts prior to the release, the subject lost accurate sense of distance to the mat.) In the first two trials, when the foot proprioceptors were left intact, the individual readily regained balance upon contacting the floor. However, in the third trial, the foot proprioceptors were anesthetized by submerging them in ice water for 20 minutes. Upon contacting the floor during this trial, the individual immediately crumbled to the mat since reflexive extension of the lower extremity did not occur. It is clinically significant that shoes inhibiting abduction of the digits (such as pointed dress shoes) may also inhibit the positive supporting reaction (268). In addition to the stability afforded by the muscle and joint proprioceptors, the importance of skin proprioceptors (e.g., Meissner’s corpuscles) was demon strated in an interesting study by Robbins et al. (269). These researchers
prove that reflex response to noxious stimulation of the plantar cutaneous receptors varies with the location of the stimuli. For example, stimulation of the skin under the metatarsophalangeal joint produces reflex contraction of the digital plantarflexors (which allows for a redistribution of ground-reactive forces away from the metatarsal heads toward the distal digits), while stimulation of the skin under the medial longitudinal arch has the opposite effect in that it causes the digits to reflexively dorsiflex (which shifts pressure from the distal digits to the metatarsal heads). Robbins et al. (269) contend that inappropriate use of arch supports may result in stimulation of the skin beneath the medial longitudinal arch, thereby exposing the metatarsal heads to trauma, as the digits are no longer able to plantarflex with full force. They also contend that excessive cushioning placed beneath the metatarsal heads may reduce the proprioceptive information supplied by skin receptors, thereby lessening the plantarflectory force developed by the digits. Because of their research findings, Robbins et al. (269) claim inappropriate stimulation of the skin receptors beneath the arch and/or excessive cushioning beneath the metatarsal heads may result in a “pseudoneurotrophic arthropathy” of the metatarsopha langeal joints. They support this hypothesis by noting that shod populations have a greater incidence of osteoarthrosis at the metatarsophalangeal joints, while unshod populations have a greater incidence of osteoarthrosis at the distal interphalangeal joints (270). In addition to improving the quality and quantity of proprioceptive input by walking barefoot, information from mechanoreceptors in the skin may also be enhanced with various adhesive taping techniques. Although studies report different outcomes, some research suggests taping may play a role in injury prevention by increasing afferent information from skin mechanoreceptors, thereby improving proprioceptive input associated with movement. Given the delicate balance between afferent and effer ent discharges, it should be clear that even slight impairment of the proprioceptive system will detrimentally affect the subsequent motor response. The impaired motor response may result in injury, as the muscular reaction to a given stimuli may occur too late to protect the joint. In fact, Lentell et al. (271) demonstrate that individuals with recurrent ankle sprains usually present with proprioceptive deficits, not strength deficits, as is most commonly reported. Impaired proprioception may also be responsible for more subtle symptoms, because some research suggests that muscle activity during the gait cycle is maintained by a centrally generated neural locomotor pattern (which exists primarily at local spinal levels) that is dependent upon the proprioceptive input associated with rhythmic limb movements (272). In describing this relationship, Rowinski (273) states that aberrations of joint proprioceptors may “disrupt the phasic relationships between feedback and the central pattern” and produce symptoms such as the inability 239
Human Locomotion: The Conservative Management of Gait-Related Disorders to develop high velocities and accelerations during the gait cycle, an increased sense of effort in the control of gait, and an increased amount of total conscious involvement in the function of ambulation. This information is of obvious importance to the running athlete. Miller et al. (313) prove convincingly that neuromotor control of the gait cycle occurs at the spinal level by placing a decerebrate cat on a treadmill (the cerebral cortex had been surgically removed). When the treadmill was turned on, the cat began walking with a normal gait, confirming spinal reflex loops control locomotion. While damage to the proprioceptive system may be the result of peripheral neuropathy or posterior column disease, more common causes for impaired proprioception include prior injury, the presence of high or low arches, and/or advanced age. Sprain/strains are notorious for affecting proprioception, since these injuries frequently damage mechanoreceptor sensory fibers producing chronic injury secondary to a delayed muscular response. As demonstrated by Hass et al. (274), even minor sprains are capable of altering supraspinal motor control because the central nervous system essentially rewires movement patterns to compensate for the injury. The authors emphasize that adaptations to supraspinal motor control are important contributors to chronic injury, and that rehabilitation specialists should treat chronic injuries by focusing on the central, not just the peripheral component of soft tissue injuries. Alterations in supraspinal motor control mechanisms may explain the frequent finding that the single best predictor of future injury is prior injury (275,276). Because compensation for even minor injury may trigger a new state of centrally generated motor control, the rehabilitation process should attempt to resolve the acute stage as quickly as possible, emphasizing the restoration/maintenance of proprioception. To be comprehensive, in addition to balance training and agility drills, various manual techniques should be incorporated to maintain flexibility and enhance proprioceptive feedback. According to Cyriax (277) and Hammer (220), cross-friction massage can improve extensibility and function of injured muscles and ligaments by lengthening fibrotic scar tissue. When done properly, cross-friction massage favorably stimulates mechanoreceptors and may produce a temporary anesthesia that is helpful in identifying the specific muscle/ligament responsible for perpetuating a chronic pain pattern. Manipulation/mobilization may also enhance proprioception by stimulating mechanoreceptors in the joint capsule. As suggested by Hiss (170), joint hypomobility produces a certain degree of “tissue tension” that forces the individual to alter the progression of forces through the plantar foot. The author claims the resultant tissue tension may interfere with the synchrony of pivoting and balancing movements that over time may result in an abnormal pattern of motor recruitment that is eventually
reprogrammed into the central nervous system. Hiss (170) claims the only effective treatment in this situation is to restore flexibility to the dysfunctional joints with the appropriate manipulative techniques. The fact that manipulation can favorably modify the transfer of forces through the foot was recently demonstrated by LopezRodriguez et al. (251). By performing a placebo-controlled study of 52 female field hockey players presenting with grade 2 ankle sprains, these authors determined that ankle manipulation produced a clinically significant redistribution of load throughout the foot, as measured with stabilometric and baropodometric techniques. In addition to injury, proprioceptive input may also be affected by arch height. As verified by Tsai et al. (198), individuals with high or low arches have impaired proprioception compared to neutral foot types, but for different reasons. According to Hertel et al. (278), because the plantar surfaces of high-arched feet typically make less contact with the ground (Fig. 4.198), mechanoreceptors in the skin provide less information regarding the distribution of pressure, which may detrimentally affect balance. It is also possible that the natural joint stiffness associated with high arches reduces mechanoreceptor input from the joint capsules and supporting soft tissues, making it difficult to balance effectively. The generalized hypomobility present in high-arched feet also makes it difficult for the body to adjust to center of mass perturbations, potentially causing the body to rely more heavily on movements of the proximal joints of the lower extremity. All of these factors may explain why individuals with high arches, compared to subjects with neutral arches, demonstrate significantly greater center of pressure excursion velocity during singlelimb stance balance tests (278).
Figure 4.198. Compared to the neutral foot (A), the high-arched foot (B) makes significantly less contact with the ground.
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Chapter Four Abnormal Motion During the Gait Cycle Individuals with low arches are also more likely to present with balance deficits. The impaired proprioception in this situation is partly due to joint laxity, which produces a passive instability that increases dependency on muscular restraining mechanisms. Because the various foot joints in low-arched individuals frequently move to their end-ranges of motion, muscles stabilizing these joints are often placed in fully stretched positions, making it difficult for them to generate adequate force; i.e., the Weber paradox states that muscles are weakest when they are fully stretched. In addition, pain fibers located in the joint capsules of hypermobile joints are more likely to discharge when the joint moves near its end-range, potentially causing a temporary neurological inhibition of the supporting muscles (which would obviously affect balance). The fact that pronated feet possess diminished proprioception was confirmed by Tsai et al. (198), who used force plate analysis during single-limb, closed-eye stance and determined that low-arched individuals have significantly greater maximum displacement in the anterior-posterior direction, use more trials to complete force plate testing, and have shorter single-limb stance duration than neutral arched individuals. When impaired proprioception is associated with high arches, manual therapies to improve overall joint excursions should be considered. This should include ankle rock board exercises, stretches to restore flexibility and manipulation to increase joint range of motion. The importance of maintaining subtle intertarsal motions is evidenced by the fact that individuals with certain tarsal coalitions are unable to balance effectively on one foot and that even a few manipulations have been shown to have a positive effect on the distribution of the center of pressure through the foot (251). Restoration/improving mobility to a stiff joint may have a facilitatory effect on the vestibular apparatus (which improves motor activity) and may even block a chronic pain pattern that may be perpetuating an injury; i.e., stimulation of the faster A-beta fibers responsible for transmitting information from joint proprioceptors will “close the gate” to the slower A-delta and type C fibers responsible for pain transmission. A perfect example of how pain and decreased proprioception may produce a chronic pain pattern occurs with reflex sympathetic dystrophy. Although the exact mechanism remains poorly understood, it is believed that nociceptive input associated with a relatively mild injury excites the internuncial neurons in the gray matter of the cord. These neurons then initiate a reverberating cycle that excites the anterior horn cells (producing muscle spasm) and lateral horn cells (producing sympathetic vasomotor and sudomotor responses). The increased sympathetic discharge may perpetuate the dystrophy, as it leads to trophic changes in the involved bone and connective tissues that further stimulate the nociceptive afferents, thereby irritating the already hyperexcited internuncials.
As explained by Korr (279), the peripheral afferents and aberrant sympathetic discharge become “reflexively coupled to their mutual detriment.” By stimulating the faster position sense joint proprioceptors immediately after an injury, manipulation is often able to break this dangerous cycle, thereby pre venting the characteristic trophic changes. Information from the nociceptive afferents may also be blocked by stimulating cutaneous receptors either manually or with tape. This explains why scratching a mosquito bite lessens the itch and why taping a painful knee lessens discomfort. In fact, many of the intricate taping procedures designed to realign the patella (e.g., the McConnell technique) have no effect on patellar positioning, yet produce significant reductions in discomfort by stimulating cutaneous mechanoreceptors. The stimulated mechanoreceptors compete with pain fibers while also supplying additional information concerning joint position/acceleration. This improves function by allowing for a more appropriate motor response. When proprioceptive deficits are the result of a pronated foot, treatment with an over-the-counter or prescription orthotic should be considered. By lessening access to the end-range of motion, orthotics may enhance the quality of proprioceptive information by improving the mechanical efficiency of the supporting muscles and lessening potential irritation from ab normally stressed joints. The ability of orthotics to favorably stimulate proprioception was demonstrated by Novick and Kelley (280). These authors measured calcaneal eversion during static stance and while walking and confirmed that orthotics more effectively limit motion when walking; i.e., orthotics decreased calcaneal eversion 2.4° during static stance and 4.2° during the gait cycle. The authors sug gest the decreased range of calcaneal eversion during locomotion results from “improved tactile and proprioceptive feedback” during dynamic function. Although some studies show no improvement in the ability to balance while wearing orthotics (281), Sloss et al. (282) demonstrate that functional foot orthoses reduce mediolateral and antero-posterior sway in subjects balancing on a pressure platform. The authors state “while foot orthoses have been used for the relief of symptoms either within or extrinsic to the foot, they could have a much wider role in the management of patients with stability problems.” Advanced age also has negative effects on proprioception. Just as hearing and sight lessen with age, mechanoreceptors provide less detailed information as we get older (283). Reduced input from mechanoreceptors plays an important role in the increased prevalence of falls present in older populations, as proprioceptive deficits associated with aging are pervasive (284). To improve balance in the elderly, Priplata et al. (285) suggest using vibrating insoles that theoretically increase input noise to the proprioceptive system, which has been shown to 241
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Figure 4.227. Alternate hip external rotator home exercise. Again with the hip slightly flexed and the knee bent 90째, the sidelying patient is positioned with the involved ankle hanging off the edge of the support surface. The hip external rotators are exercised by raising and lowering the weighted ankle.
Figure 4.228. Gluteus medius home exercises. The sidelying patient is positioned near the edge of a support surface with the involved hip adducted (i.e., the ankle is lower than the support surface). The posterior fibers of gluteus medius are exercised by raising and lowering the straight lower extremity through a full range of motion (the hip is abducted and adducted approximately 45째 in each direction). To strengthen the anterior fibers of gluteus medius, the same maneuver is performed with the involved hip extended, so the straight lower extremity is hanging off the back edge of the support surface. This exercise was found to be superior to the clamshell exercise for recruiting the gluteus medius muscle (335).
Figure 4.229. Upper hamstring exercise. The standing patient is positioned with arms crossed and the toes of the uninvolved leg lightly touching the ground. There is minimal body weight placed on the uninvolved leg as the distal toe contact point is used for balance only. To exercise the upper hamstring fibers, the patient tilts the upper body forward, pivoting at the hips. In order to isolate the upper hamstring, the lumbar lordosis is maintained throughout this motion. By tilting the upper body away from involved side, the bicep femoris muscle is more vigorously stimulated. The intensity of this exercise may be increased by having the patient hold a weighted plate between his or her crossed arms.
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Figure 4.230. Lower hamstring exercise. The lower hamstrings are exercised having the standing patient support his/her upper body on a stable surface while alternately raising and lowering the weighted ankle. By duplicating the joint angles present during late swing (i.e. the hip is flexed lightly as the knee is extending) this exercise teaches the hamstring muscles to decelerate forward motion of the swinging leg. To isolate specific fibers of the medial and lateral hamstrings, the leg is slightly internally and externally rotated.
Figure 4.231. Physioball hamstring exercise. With arms fully abducted for stability, the supine patient flexes and extends his/her knees while pulling and pushing a physioball forward and backward (arrow). Throughout this exercise, the spine is maintained in a neutral position.
Figure 4.232. Single-leg physioball hamstring exercise. This is a more advanced exercise as it requires both strength and balance. The supine patient points the straightened uninvolved lower extremity towards the ceiling while pulling and pushing the physioball with the involved leg. Again, the spine is maintained in a neutral position.
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Figure 4.234. Standing gluteus medius exercise. With the hips flexed and abducted 20°, the standing patient repeatedly abducts the knees against resistance provided by a TheraBandŽ .
Figure 4.233. Hip external rotator/posterior gluteus medius exercise. The standing patient stabilizes the upper body on a stable surface and extends the uninvolved hip so the straight lower extremity parallels the spine. While maintaining the spine in a neutral position, the muscles of the involved weight-bearing hip raise and lower the contralateral pelvis. In this illustration, the hip external rotators of the left lower extremity are working to raise and lower the right hip. It is important that the contralateral leg does not flex and extend, as the motion is performed with the muscles of the weight-bearing hip. This maneuver serves as an excellent in-office test of hip external rotator endurance.
Figure 4.235. Lunge exercise. The classic lunge exercise is performed on a stable surface with the patient stepping either forward or backward. To enhance proprioception, a lunge may be performed by stepping onto an unstable surface, such as a Dyna disc (www.performbetter.com). Although not illustrated, squats are also useful for strengthening the quadriceps, but because of the high retropatellar pressures associated with squat maneuvers (up to 7 times body weight), they should be used cautiously. A simple method to lessen retropatellar pressures while performing a standard lunge is to have the patient get into the end position of a long-step forward lunge, and then raise and lower the pelvis while keeping their feet in the maximally separated position (336).
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Figure 4.236. Thera-Band® leg press. By having the patient perform conventional leg presses while externally rotating the lower extremities against resistance provided by a Thera-Band®, coactivation of gluteus medius and gluteus maximus is enhanced. To lessen retropatellar pressures, this exercise may be performed through the final 30° of knee extension.
Figure 4.237. Gluteus maximus kickbacks. With the patient resting on all fours and a weight placed around the involved ankle, gluteus maximus and the hamstring muscles are exercised by performing repeat kickbacks.
Figure 4.238. Bird dog exercise. The patient is resting on all fours and extends alternate arms and legs. This exercise is a safe and effective way to recruit the hip and spinal stabilizer muscles. McGill (337) demonstrates that moving the extended arms and legs in 4-inch squares enhances activity in the external obliques, latissimus dorsi, erector spinae, gluteus medius and gluteus maximus muscles. The squares are performed by moving only the hip and arms, and the spine should be maintained in a fixed position.
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