Abstract: A first prosthetic part (11) is adapted to be attached to a femur; a second prosthetic part (17) is adapted for attachment to the tibia. An intermediate joint assembly has a meniscal part (13) and a coupling part (15) which is rotatable about an axis of rotation (39). The femoral part and an element of the intermediate joint assembly, respectively, have rotary joint surfaces (19, 21) which are essentially congruent. To permit the intermediate joint assembly to move in translatory direction in addition to rotation thereof about the axis (39), the assembly includes a guide portion (16) engaging a guide track(35), preferably formed on the meniscal and coupling parts, respectively. The guide track and the guide portion are interlocked, for example by forming the guide track and the guide portion in dovetail, tongue-and-groove connection, or the like.

Abstract: To permit movement of coupling elements (13, 13a, 13b) which carry joint surfaces (21) congruent with condylar portions (19) of the prosthesis, the coupling elements are slidable in guide tracks (35), which are curved, and are widened at their terminal portions. The coupling elements have elongated engagement ribs which fit into the guide track groove, with minimum clearance and play at the narrowest, central portion of the guide groove, while permitting limited twisting as well as sliding movement due to the widened regions of the guide track at its end region. The position of guide track-rib can be reversed, if desired. The elements slide on a slide surface and can be retained, for example by an interlocking connection, such as a dovetail.

Abstract: When the knee bends, the condyle-like bearing surfaces of the femur part of the prosthesis slide on the tibia-like rolling surfaces of the tibia part. The motion is guided by a web of the tibia part which engages in a fork-like mounting of the femur part. The web has a head which has a cylindrical shape to slide on a corresponding cylindrical section formed by a member mounted in the femur part. Web and mounting are preferably made of metal whereas the member in the femur part is made of another material, preferably, a moulded plastics member.