Patent ID: 8529634

Claim:
A prosthetic limb comprising a knee joint composed of a multiple-link mechanism and adapted to make an upper member and a lower member movable about an instantaneous rotational center of rotation, and drag generating means composed of a hydraulic cylinder or a spring cylinder, said drag generating means being pivotably attached to said multiple-link mechanism and adapted to produce a drag for restraining deformation of said multiple-link mechanism, said drag generating means being in a specific arrangement with respect to said multiple-link mechanism, accordingly, during the swing phase of one cycle of a walking form, a relation of T1<T2 being satisfied wherein T1 is the first torque about the instantaneous center of rotation at the first stage of initial period of bend of knee joint and T2 is the second torque about the instantaneous center of rotation at the second stage of final period of the further advanced bend of knee joint, and wherein said drag generating means is in such an arrangement that the length L1 of a lever arm at the first stage of initial period of bend of knee joint is smaller than the length L2 of a lever arm at the second stage of final period of bend of knee joint, wherein the bend of knee joint comprises a bending angle, wherein said multiple-link mechanism comprises a constrained chain comprising at least four links rotatably coupled to each other at a fixed separation distance, wherein said upper and lower members are one of the links which compose said multiple-link mechanism, and said drag generating means is attached to said multiple-link mechanism at two positions, an upper attachment position with respect to said upper member and a lower attachment position with respect to said lower member, wherein the upper attachment position of said drag generating means is located on a line, or on an extension of the line, which line connects said upper and lower attachment positions with the instantaneous center of rotation when the bending angle at the first stage of initial period of bend of knee joint is arbitrary.