Rotating/sliding contrained prosthetic knee

Claim 1

An improved prosthetic device for performing the function of a knee joint between the femur and tibia bones of a human, each having a generally longitudinal axis, comprising: femoral attachment means adapted for attachment to the femur, said femoral attachment means including a stem portion for insertion .into the femur and a base portion, said stem being removable from said base, and means to secure the stem to the base; a pair of depending, convex bearing surfaces on said base portion of said femoral attachment means; tibial attachment means adapted for attachment to the tibia, said tibial attachment means including a generally hollow, depending stem and a generally flat platform portion; a planar bearing surface on the platform portion of the tibial attachment means, said planar bearing surface generally at right angles of the longitudinal axis of said tibia; hinge means for connecting said femoral attachment means to said tibial attachment means for rotation about an axis generally perpendicular to the longitudinal axis of the tibia, said hinge means including a pair of medial-lateral spaced apertures in the base portion of the femoral attachment means, a hinge pin, and a yoke having an aligned, medial-lateral aperture for receiving said hinge pin; a bearing element between said convex bearing surfaces and said planar bearing surface and having a pair of generally concave surfaces on one side for engaging said convex surfaces and an opposite, generally flat side, mating in congruent bearing relationship with said planar bearing surface; and means for mounting the bearing element on the tibial attachment means to permit rotary and sliding movement between the bearing element and the planar bearing surface, said mounting means including an elongated aperture in the bearing element for engaging the medial-lateral exterior surfaces of said yoke portion of the hinge means to permit translatory movement generally in the anterior-posterior direction and a depending bearing shaft on the yoke for insertion into the hollow stem of the tibial attachment means to permit rotary movement of the yoke; whereby said bearing element is freely rotatable through a prescribed arc in a plane approximately perpendicular to the longitudinal axis of said tibia and slideable relative to said tibia to permit natural movement between the femur and tibia.