Artificial leg with stable link-type knee joint

Claim 1

An artificial leg comprising an upper leg stump socket portion and a shin portion in which a rearwardly and downwardly sloped plate within the shin portion is connected to a substantially horizontal plate at the base of the socket portion by a forward pair and a rearward pair of pivoted links, the links of said forward pair being shorter than the links of said rearward pair, said forward and rearward pairs of links connected to said horizontal plate and to said sloped plate by pivots, the pivots on said sloped plate being spaced apart by more than twice the distance separating the pivots on said horizontal plate, with the pivots on said horizontal plate disposed at intermediate positions relative to the horizontal positions of the pivots on said sloped plate when the leg is in a fully extended positiOn, said pairs of links jointly forming an articulation between said socket and shin portions and having an instantaneous center of rotation constituted by the intersection point of a line drawn through the pivot points of a forward link and a line drawn through the pivot points of a rearward link, said center of rotation being located in substantially the region of that of a natural knee and lying upon a curve which is ascending through approximately 15* of relative rotation between said socket and shin portions of the leg from the fully extended position, said articulation exhibiting flexure exceeding 90* to enable natural sitting posture.