Prosthetic device

A knee joint prosthesis comprising a patella prosthesis for sequential articulation against the condylar surfaces and the surface of the central medially-laterally flat and longitudinally convex groove in an anterior flange bridging said condylar surfaces of a femoral prosthesis having a central opening therein for passage of the cruciate ligaments, said patella prosthesis comprising a substantially flat base, having an outline comprised of two parallel sides and semicircular end portions, one surface of which is adapted for attachment to the resected surface of the natural patella, a bearing insert having a peripheral outline substantially coextensive with said base and having a central laterally extending medially-laterally flat and longitudinally concave ridge portion adapted for sequential tracking within the medially-laterally flat and longitudinally convex groove in the anterior flange of said femoral prosthesis and a pair of shoulders having a shape complementary to the condylar surfaces of said femoral prosthesis for sliding contact with said surfaces during flexion of the knee joint, said central laterally extending medially-laterally flat and longitudinally concave ridge portion and said pair of shoulders thus providing medial and lateral stability to the patellar prosthesis.