An artificial knee joint that includes a femoral component with a specially shaped bearing surface and a tibial component, whose surface interacts with the femoral surfaces. The interaction provides for the required motion and stability characteristics. The interaction between the femoral and tibial surfaces is such that as the knee is flexed to maximum, the femoral component moves posteriorly on the tibial surface, by an amount similar to that in the anatomic knee. This is accomplished primarily by the depth and width of the femoral trochlea diminishing as the femoral component is flexed from zero to maximum, together with a ramp on the center of the tibial surface. The opposite motion, roll forward of the femur from a fully flexed to a more extended position, is accomplished by varying the outward radii of the lateral and medial femoral bearing surfaces, together with a ramp on the postero-lateral and postero-medial regions of the tibial surfaces. A variation of this is to generate a tibial surface which provides for a progressive internal rotation of the tibia as flexion proceeds.
