Abstract: A novel knee prosthesis is disclosed comprising a femoral component and a tibial component adapted respectively to be secured to the adjacent ends of the femur and tibia, with each component comprising a spaced pair of bearing portions for articulation of the knee in the sagittal plane. A first guiding surface carried by the femoral component cooperates with a second guiding surface carried by the tibial component to induce posterior movement of the contact area of the femoral bearing portions upon the tibial bearing portions with increasing flexion of the knee. The two guiding surfaces are preferably located in the intercondylar region. The prosthesis may also be adapted for use in other joints, e.g. the elbow.