A bicondylar implantable prosthesis resurfaces only the weight bearing portion of the patients femur. The prosthesis includes a thin shell convexly curved outer articular surface including a medial condyle, a lateral condyle, and an intercondylar bridge, and a concave inner surface of the prosthesis that has at least one transverse ridge extending across the width of the prosthesis. When the prosthesis is implanted on the weight bearing portion of the femur, the entire outer surface of the curved articular surface is sized to resurface substantially only the weight bearing portion and no portion of the patello-femoral joint of the knee. The prosthesis is configured to be implantable by a lateral insertion through a direct lateral approach to a retropatellar region of the patients knee joint, during which insertion the at least one transverse ridge guides the prosthesis along a laterally resected surface of the femur.
