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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

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Hydraulic prosthetic knee mechanism

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

ABSTRACTProsthetic 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. Thesaid Mechanism is developed based on hydraulics

principles which avoid wear and tear of the

material and the friction within it. Hydraulicfluid 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 consideredfor modeling the mechanism are taken based on

the size of the amputated knee.

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

I. INTRODUCTIONIn orthopedic medicine,

prosthesis, prosthetic, or prosthetic limb is anartificial device extension that replaces amissing body part. It is the science of

using mechanical devices with human muscle,skeleton, and nervous system to assist or enhancemotor 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. Prostheticlimbs are incredibly valuable to amputees because prosthesis can help restore some of the capabilitieslost with the amputated limb. The human leg is acomplex and versatile machine. Designing a

prosthetic device to match the leg’s capabilities is aserious challenge. Team of scientists, engineers anddesigners around the world use different approachesand 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 suctionsock 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 providesfriction 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 functionand in appearance. In recent year’s usage of

computers in prosthesis have been increased.Modeling of prosthetic limbs is done using Pro-Engineer software. Various components of prosthetic knee are designed and assembled. This

work involves development of a design which playsthe 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 patientsare 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 articulationthey provide and the means of controlling thearticulation. Articulation can be single-axis or

polycentric. Stance-phase control, helping to keepthe leg from buckling when loaded, can be achievedin several ways including the alignment of

prosthetic components, manual locks, weight-activated stance mechanisms, mechanical friction,fluid resistance, and polycentric mechanisms. Many

knee joints incorporate a combination of these.Swing-phase control influences toe-clearance andthe degree of knee flexion, and can be implementedusing mechanical friction, pneumatic or hydraulic

mechanisms or a combination of these. In manycases, energy--storing components such as springsare also used to complement swing-phase control.

Below figure shows some of the availabledesigns in prosthetic knee joints which usesdifferent mechanisms to retain original knee motion.

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III. FUNCTIONING OF KNEETo design an artificial knee which

resembles that of original knee first one has tounderstand function of knee joint in human body.

The knee joint joins the thigh with the leg

and consists of two articulations, one betweenthe 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 slightmedial and lateral rotation. Since in humans theknee supports nearly the whole weight of the body,it plays an important role in humans to walk andrun.

The function of the knee is to provide

stability and flexibility to the lower leg whilewalking, running, and stair climbing, rising from aseated position. It moves in bending, straightening,

and rotation.

Above figure shows gait cycle of right legin normal human. Stance phase is a period where leg

will be in free position where forces acting will be

negligible on knee. Swing phase is a period wherewalk will depend on controls of knee mechanism. Ininitiation 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 donot provide all of above mentioned functions but

can be flexible for walking as normal human.

IV. PROPOSED DESIGNAlthough many mechanisms are available,

it is human nature to search for better one based oncomfort and ease of flexibility. Mechanism designedis by using hydraulics. Hydraulic fluid in between

joints in mechanism provides the required motion of a knee by compression and expansion whileapplying load. Constraints provided to themechanism are based the degrees of freedom of knee. Major function of this mechanism is to bendcertain amount when load is applied and regain to its

original position when load is released. Proposeddesign is flexible because of simple mechanisminvolved, no wear and tear due to usage of hydraulicfluid, 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 prostheticknee joint. Knee joint plays a vital role in whole leg.The general operation of a prosthetic knee is a basiclock - unlock mechanism that corresponds tostraightening and bending of a knee. Traditionally, a prosthetic knee would lock when the foot touches

the ground and it would unlock when the toe pushesoff 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 expandswhen load is removed. Based on this property of

fluid this mechanism has been developed.

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Fig 4.1 Exploded view of mechanism showingindividual 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 beconnected to prosthetic foot.

Fig 4.2 Assembled view of mechanism

The above figure shows position of kneewhen leg is in stance position. Main working of this

mechanism lies in the central part i.e., arc whichconsist of combination of upper and lower part.When knee rotates about axis of pin lower part willmoves along arc of upper part. Hydraulic fluid is

placed in hallow place which present betweenrevolving part combination of upper and lower

parts.

Red and green lines show in figure givesthe information about the place of hydraulic liquidto be placed.

4.1 WorkingHydraulic liquid in central part locks the

knee when leg is in stance phase. Whenever load isapplied on toe in swing phase lower part willrevolve along the axis of pin. Since hydraulic fluidin central part don’t allow to compress over 90

degrees lower part will revolve only up to certainangle which is suitable to transfer for heel-risecontrol to terminal stage in swing phase. Due to

compression hydraulic fluid may exert more amountof force which may cause vibration in knee joint so placing some hydraulic liquid above lower arc ( Redlines in fig) reduces the vibration in knee joint when

returning to its original position.

Above figure gives the completeinformation of working of mechanism likemovement of lower part from stance to swing phase

and swing phase to stance phase.

V. CONCLUSIONThe above proposed design regarding the

structure of the knee is worked towards movementof knee. Extension of this work by connecting it

with the prosthetic foot will make one of the humanachievements in alteration process of walking.Successful extension of this project in proposedmanner can be applied in medical practices,

representing the combination of advance mechanicaland medical technologies.

R EFERENCES [1] Development of prosthetic knee joint

technologies for children and youth with

above-knee amputations by Prof.

.Dr.. Macarthur, University of Toronto.[2] Alternate materials for prosthetic leg by

Y.Kalyan Chakravarthy. [3] Design and analysis of prosthetic knee

joint by Prof. W. L. Cleghorn & J.

Andrysek

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