Abstract: A hip prosthesis includes a straight shaft which is to be inserted into the femur, the straight shaft including a proximal part that is configured to be inserted in the metaphyseal region of the femur. The proximal part has, on each of its front and rear faces, at least one projecting fin with a steep medial flank that deviates at least over part of its length away from the longitudinal direction of the shaft. At its top the proximal part is inclined toward the femoral neck. In this way, when the shaft is driven into the bone, the bone substance surrounding the fin is compacted and is able to absorb greater forces. The height of the fin decreases from its medial flank toward its lateral edge.

Abstract: A knee prosthesis includes a femoral prosthetic part which forms a pair of condylar gliding surfaces, a tibial part that has tibial gliding surfaces cooperating with the condylar gliding surfaces and a coupling part that connects the femoral and tibial parts so that they can rotate about a rotational axis that is approximately parallel to the axis of the tibia. If the femoral and tibial parts have the same anteroposterior alignment, an applied load is borne by a central region of the tibial gliding surfaces. The tibial gliding surface slopes upwardly relative to the prosthesis both in front of and behind the central region of the tibial gliding surface so that when the femoral and tibial parts rotate against one another, each of the condylar gliding surfaces remains in contact with its corresponding tibial gliding surface.