Bronson, DVM: Stifles

By Dr. Joanna Bronson | http://bronsonvetservices.com/

A horse's stifle joint is comparable to a human knee. It has a kneecap with attached ligaments for structural stability although the horse's stifle joints are located on their hind limbs.

Surrounding the joint is a thin fluid-filled capsule that assists with shock absorption and lubrication. The side ligaments function like their human counterparts to stabilize the joint and prevent it from bending too far in either direction.

When the stifle joints are working properly, the horse is stable in his movements. Trauma can lead to stifle injuries.

Signs of a possible stifle injury may include a combination of swelling, lameness, a lack of tolerance for exercise, kneecaplocking, and joint thickening. Once the stifle joint is compromised, the horse may demonstrate any or several of these signs: Ÿ Toe dragging Ÿ Canter resistance or a very rough canter Ÿ Difficulty backing up Ÿ A shortened stride

Ÿ Issues going up and down hills Ÿ Drifting to one side over fences Ÿ Problems transitioning from trot to canter and vice versa A horse showing stifle lameness will often be likely to have a sore back or croup.

Some stifle issues may emit a clicking sound which could indicate a rupture of the cartilage or ligaments.

Stifle diseases are classified as being either acquired or developmental disorders.

Acquired disorders happen to the horse. They include arthritis, degenerative joint disease, ligament injury, bone chips, inflammation, fractures, and trauma. These issues can result from infection, bacteria, or from an injury. Acquired disorders usually develop suddenly with obvious lameness and swelling. Arthritic development is often secondary to a long-term injury.

Developmental disorders are often inherent and can be present at birth as the result of genetic abnormalities. Horses with straight hind limbs, OCD lesions, and hooves with low heels and long toes are more at risk for developing stifle problems.

Foals and young horses may show subtle signs such as swelling and low-level lameness as the horse begins training. The signs will decrease as activity decreases.

Developmental disorders include osteochondritis dissecans (appearing within the first 6 months), subchondral bone cysts, and patellar luxation. The origin of bone cysts is not always clear, but trauma or another disorder of the bone or cartilage may be a contributing factor.

Meniscal tears can occur in horses. The severity of the tear determines the severity of the lameness. Stifle injuries can result from direct trauma or stress such as experienced in certain disciplines that involve quick directional changes, fast stops, and repeated jumping. Horses involved in showing, and working horses used for roping, cutting, barrel racing, harness racing, eventing, and upper-level dressage are particularly susceptible to stifle injuries.

Diagnosing a stifle problem involves a physical examination (including a flexion test and examination for swelling), digital x-rays (to show the existence of arthritis, bone cysts, or fractures), ultrasound and curvilinear ultrasound probes to show ligament or muscle injuries.

Treatment will depend on the specific injury or disease. A period of 2 to 3 months of rest might be prescribed to alleviate swelling and giving the joint a chance to heal if the joint capsule is stretched and not ruptured. If inflammation is present, intra-articular medicine may be prescribed.

Horses with mild stifle lameness may respond to rest and the use of non-steroidal anti-inflammatory drugs (NSIAIDs), or injections of corticosteroid and hyaluronic acid to counteract inflammation. Equines that have had soft tissue abnormalities eliminated during the exam may be candidates for arthroscopy (a minimally invasive diagnostic procedure). Corrective shoeing where the farrier either trims the inside wall or applies a lateral heel wedge to encourage hoof rotation can also help with stifle-locking problems.

Another treatment involves the use of estrogen which is injected into the stifle to increase ligament tension.

Platelet-rich plasma (PRP) has been used to encourage healing in soft tissue injuries. The horse's own blood is harvested, and the PRP is then removed in a centrifuge and reinjected into the soft tissue. Stem cell treatments have proven beneficial. The stem cells from the animal's fat or bone marrow are collected, processed, then reinjected into the stifle joint. Non-invasive shock wave therapy treatments have shown promising results for both bone and soft tissue healing.

The prognosis for healing varies with each individual and is usually determined by age, degree of lameness, duration of lameness, and the presence of partial-thickness cartilage lesions.

Effective management techniques are beneficial. Affected horses need lots of turnout to encourage movement, strengthening exercises in the saddle or in hand, regular uphill and other groundwork while foremost maintaining a healthy weight. Dr. Joanna Bronson graduated from MSU College of Veterinary Medicine at the top of her class. In 2005, she opened Bronson Veterinary Services in Coldwater, MI, a full-service equine, small animal hospital and surgical center. Bronson Veterinary Services also has a mobile unit for equine calls and after hour emergency care.