Knee joint prosthesis

Claim 1

A knee joint prosthesis comprising a femoral component adapted to be implanted on the condylar portion of the femur and having a pair of laterally spaced-apart condylar portions, each of which has an external surface that is smoothly convexly curved in the antero-posterior direction and generally matches the shapes in lateral profile of the condylar surfaces of the femur and that is smoothly convexly curved in all cross sections along its antero-posterior extent, and a box-like intercondylar portion interconnecting the condylar portions and defining an intercondylar recess having spaced-apart lateral surfaces, an anterior surface and a posterior surface; and a tibial component adapted to be implanted on the tibial plateau and including a plate-like platform portion having on its superior surface a pair of laterally spaced-apart concavities, each of which is adapted to receive in nested relation one of the condylar portions of the femoral component, and a post extending superiorly from the platform portion which is adapted to be received in the intercondylar recess of the femoral component, the post having lateral surfaces, an anterior surface and a posterior surface, the relative positions and shapes of the anterior surfaces of the post and recess of the prosthesis as implanted in the knee joint being such that when the leg is at and near full extension and the femur tends to dislocate posteriorly relative to the tibia, the anterior surfaces engage each other to prevent posterial dislocation of the femoral component and when the leg is partly flexed the anterior surfaces are spaced from each other and permit relatively free relative antero-posterior translation of the components but restraining excessive anterior and posterior movements, the relative positions and shapes of the posterior surfaces of the post and recess of the prosthesis as implanted in the knee joint being such that when the leg approaches full flexure and the femur tends to dislocate anteriorly, the posterior surfaces engage each other to prevent anterial dislocation of the femoral component and when the leg is partly flexed or is extended the posterior surfaces are spaced-apart and permit essentially free, relative antero-posterior translation of the components, and the adjacent lateral surfaces of the post and recess diverging superiorly relative to the platform portion of the tibial component to permit essentially free normal lateral angulation.