US Patent 7591855 Knee prosthesis with rotation bearing

A knee prosthesis including a femoral component, a tibial component and an intermediate piece which connects these forming a flexion bearing with the femoral component and a rotation bearing with the tibial component, which rotation bearing can be locked relative to the tibial part. To allow the physician to decide during the operation whether to use a rotation-free prosthesis or a rotationally fixed prosthesis, the intermediate piece is alternatively provided with a projection which engages in a matching recess in the tibial component.