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S.V.N.Akhilesh, L.Ramesh / International Journal of Engineering Research and Applications (IJERA) ISSN: 2248-9622 www.ijera.com Vol. 3, Issue 2, March -April 2013, pp.1816-1818

Hydraulic prosthetic knee mechanism S.V.N.Akhilesh, L.Ramesh (Department of Mechanical Engineering, KL University, Vaddeswaram) (Department of Mechanical Engineering, KL University, Vaddeswaram)

ABSTRACT Prosthetic knee mechanism helps in framing a better prosthetic knee for those individuals with knee amputations in the porting above knee joint. The primary objective of this mechanism is that it should withstand the human loads, be flexible to the movements and also be able to mingle with the amputated part in the similar manner as that of the natural knee. The said Mechanism is developed based on hydraulics principles which avoid wear and tear of the material and the friction within it. Hydraulic fluid used in this mechanism helps in attaining the natural knee function. The 3D model has been created using Pro-Engineer modeling software.

The main objective of the paper is to develop a knee mechanism that is more flexible, economical, efficient, ease in manufacturing than the existing models. The dimensions considered for modeling the mechanism are taken based on the size of the amputated knee.

Keywords - Prosthetic, amputations, Hydraulic, Polycentric, congenital, Transfemoral, Articulation

I. INTRODUCTION In orthopedic medicine, prosthesis, prosthetic, or prosthetic limb is an artificial device extension that replaces a missing body part. It is the science of using mechanical devices with human muscle, skeleton, and nervous system to assist or enhance motor control lost by trauma, disease, or defect.

Prostheses are typically used to replace parts lost by injury (traumatic) or missing from birth (congenital) or to supplement defective body parts. Prosthetic limbs are incredibly valuable to amputees because prosthesis can help restore some of the capabilities lost with the amputated limb. The human leg is a complex and versatile machine. Designing a prosthetic device to match the leg’s capabilities is a serious challenge. Team of scientists, engineers and designers around the world use different approaches and technologies to develop prosthetic legs that help the user regain a normal, active lifestyle.

In 1898, Dr. Vanghetti invented an artificial limb that could move with through muscle contraction. In 1946, a major advancement was made in the attachment of lower limbs. A suction sock for the above-knee prosthesis was created at University of California (UC) at Berkeley. The

usage of ‘Hydraulics’ in designing a prosthetic knee joint has been increased in recent years, because of the reliability it provides considering to other mechanisms. Hydraulic knee joint has more flexibility, life and also ease of utility. It provides friction less motion in the mechanism developed, which improves the life of knee. Wear and tear of the parts used can be easily avoided. The prosthetic knee designed resembles human knee in function and in appearance. In recent year’s usage of computers in prosthesis have been increased.

Modeling of prosthetic limbs is done using ProEngineer software. Various components of prosthetic knee are designed and assembled. This work involves development of a design which plays the same role as that of original knee.

II. PROSTHETIC TECHNOLOGIES IN USE Prosthesis for individuals with amputations above the knee is referred to as transfemoral or above-knee prosthesis. Knee disarticulation patients are also missing the functional aspects of the knee, but their prosthesis are typically termed knee disarticulation prosthesis.

A variety of prosthetic knee joint designs exist, generally classified by the type of articulation they provide and the means of controlling the articulation. Articulation can be single-axis or polycentric. Stance-phase control, helping to keep the leg from buckling when loaded, can be achieved in several ways including the alignment of prosthetic components, manual locks, weightactivated stance mechanisms, mechanical friction, fluid resistance, and polycentric mechanisms. Many knee joints incorporate a combination of these.

Swing-phase control influences toe-clearance and the degree of knee flexion, and can be implemented using mechanical friction, pneumatic or hydraulic mechanisms or a combination of these. In many cases, energy--storing components such as springs are also used to complement swing-phase control.

Below figure shows some of the available designs in prosthetic knee joints which uses different mechanisms to retain original knee motion.

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S.V.N.Akhilesh, L.Ramesh / International Journal of Engineering Research and Applications (IJERA) ISSN: 2248-9622 www.ijera.com Vol. 3, Issue 2, March -April 2013, pp.1816-1818 negligible on knee. Swing phase is a period where walk will depend on controls of knee mechanism. In initiation phase force will be applied on toe which in turn acts on knee used to swing about axis of knee.

Many prosthetic mechanisms developed to date do not provide all of above mentioned functions but can be flexible for walking as normal human.

IV. PROPOSED DESIGN

III. FUNCTIONING OF KNEE To design an artificial knee which resembles that of original knee first one has to understand function of knee joint in human body.

The knee joint joins the thigh with the leg and consists of two articulations, one between the femur and tibia, and one between the femur and patella. It is the largest joint in the human body and is very complicated. The knee in human body permits flexion and extension as well as a slight medial and lateral rotation. Since in humans the knee supports nearly the whole weight of the body, it plays an important role in humans to walk and run.

The function of the knee is to provide stability and flexibility to the lower leg while walking, running, and stair climbing, rising from a seated position. It moves in bending, straightening, and rotation.

Above figure shows gait cycle of right leg in normal human. Stance phase is a period where leg will be in free position where forces acting will be

Although many mechanisms are available, it is human nature to search for better one based on comfort and ease of flexibility. Mechanism designed is by using hydraulics. Hydraulic fluid in between joints in mechanism provides the required motion of a knee by compression and expansion while applying load. Constraints provided to the mechanism are based the degrees of freedom of knee. Major function of this mechanism is to bend certain amount when load is applied and regain to its original position when load is released. Proposed design is flexible because of simple mechanism involved, no wear and tear due to usage of hydraulic fluid, provides long life, flexible in usage.

Any mechanism that is designed should be as in above picture. There will be a socket to which thigh is connected a prosthetic foot and a prosthetic knee joint. Knee joint plays a vital role in whole leg.

The general operation of a prosthetic knee is a basic lock - unlock mechanism that corresponds to straightening and bending of a knee. Traditionally, a prosthetic knee would lock when the foot touches the ground and it would unlock when the toe pushes off the ground and the leg swings forward. This paper deals with prosthetic knee joint which uses hydraulic fluid to retain original knee mechanism.

Hydraulic fluid has the tendency of compressing while load is applied and expands when load is removed. Based on this property of fluid this mechanism has been developed.

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S.V.N.Akhilesh, L.Ramesh / International Journal of Engineering Research and Applications (IJERA) ISSN: 2248-9622 www.ijera.com Vol. 3, Issue 2, March -April 2013, pp.1816-1818 Red and green lines show in figure gives the information about the place of hydraulic liquid to be placed.

Fig 4.1 Exploded view of mechanism showing individual parts It consists of only two main parts which will minimize the complexity in mechanism, a pin joint to assembly these both parts. Upper part will be connected to socket and lower part will be connected to prosthetic foot.

4.1 Working Hydraulic liquid in central part locks the knee when leg is in stance phase. Whenever load is applied on toe in swing phase lower part will revolve along the axis of pin. Since hydraulic fluid in central part don’t allow to compress over 90 degrees lower part will revolve only up to certain angle which is suitable to transfer for heel-rise control to terminal stage in swing phase. Due to compression hydraulic fluid may exert more amount of force which may cause vibration in knee joint so placing some hydraulic liquid above lower arc ( Red lines in fig) reduces the vibration in knee joint when returning to its original position.

Above figure gives the complete information of working of mechanism like movement of lower part from stance to swing phase and swing phase to stance phase.

Fig 4.2 Assembled view of mechanism The above figure shows position of knee when leg is in stance position. Main working of this mechanism lies in the central part i.e., arc which consist of combination of upper and lower part.

When knee rotates about axis of pin lower part will moves along arc of upper part. Hydraulic fluid is placed in hallow place which present between revolving part combination of upper and lower parts.

V. CONCLUSION The above proposed design regarding the structure of the knee is worked towards movement of knee. Extension of this work by connecting it with the prosthetic foot will make one of the human achievements in alteration process of walking.

Successful extension of this project in proposed manner can be applied in medical practices, representing the combination of advance mechanical and medical technologies.

REFERENCES [1]

[2] [3]

Development of prosthetic knee joint technologies for children and youth with above-knee amputations by Prof. .Dr.. Macarthur, University of Toronto.

Alternate materials for prosthetic leg by Y.Kalyan Chakravarthy.

Design and analysis of prosthetic knee joint by Prof. W. L. Cleghorn & J. Andrysek

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