Patent ID: 7951204

Claim:
A knee prosthesis comprising: a metal base having upper and lower surfaces, an anchoring rod extending from said lower surface for fixing said base into a tibia of a patient, a plastic tibial plate having a lower surface for engaging said upper surface of said base, said upper surface of said base including an anterior portion spaced radially ahead of a tibia bone axis (Y,Y′) when the anchoring rod is fitted into the tibia of the patient, an arcuately oriented guide structure for controlling any relative rotation of said plate and said base, said arcuately oriented guide structure defining an arc of a circle having a center of rotation (C,C′) about which said plate may rotate, said guide structure being positioned in the anterior portion of the upper surface of said base and extending upwardly from this anterior portion, and being oriented, along its arc, in a substantially medio-lateral direction and extending, along its arc, on both sides of a median plane of the base parallel to a sagittal plane of the patient and containing the tibia bone axis (Y,Y′) when said anchoring rod is fitted into the tibia of the patient, and a recess in said lower surface of said plate of an arcuate shape for cooperatively receiving said guide structure of said base such that any relative rotation between said plate and said base is determined by an arcuate length of said recess relative to an effective arcuate length of said guide structure, wherein said guide structure includes an upstand in the shape of the arc of a circle, wherein said upstand includes a central portion and two opposite side portions that extend from each medio-lateral side of the central portion and wherein said central portion extends upwardly from said upper surface of said base at a greater distance than said side portions.