US Patent 7303586 Coupled knee prosthesis with a rotational bearing

A knee prosthesis includes a femoral component with condylar sliding surfaces which are rigidly interconnected, a tibial component provided with a tibial platform which is linked to it in a non-rotatable manner and has tibial sliding surfaces which cooperate with the condylar sliding surfaces, and a coupling device which forms a flexion bearing with the femoral component and a rotational bearing with the tibial component, the axis of said rotational bearing being inclined relative to the tibial direction. In order to achieve a more advantageous force distribution in the prosthesis and a restoring force upon rotation of the prosthesis parts, the prosthesis is configured such that the normal with respect to the area of the tibial sliding surfaces which cooperates with the condylar sliding surfaces and transmits most of the load in the extension position is less inclined relative to the tibial direction than is the axis of the rotational bearing, as seen in a side view or sagittal section.