The present invention mainly relates to knee joint and more particularly to the polymeric composite or nanocomposites based polycentric knee joint. In one embodiment the knee joint comprising: a top part having a top face and a bottom face, wherein the top face having an adapter coupled firmly with the top part to transfer the load from the stump of amputee via socket, a bottom part having a top face and a bottom face, at least one middle linkage pivotably coupling a middle posterior region of the top part with a middle posterior region of the bottom part, at least two side identical linkage pivotably coupling a sides of the top part with a sides of the bottom part, a compression spring along with cylindrical rod positioned in the interior of the bottom part which provides the engaging and disengaging of the top and bottom part, at least two extension spring couples the top and bottom part through two tiny holes and through simple supported beam in the top and bottom part for the flexion and extension of the knee joint and a bumper positioned in the base of the bottom part which contacts with the pylon to absorb the vibration and the terminal impact during the hip hike.
