Knee prosthesis comprising a metal base secured to an anchoring rod for fixing it into a tibia of a patient. A plastic tibia plate is freely slidable over the base. The metal base and the tibia plate are equipped with a guide mechanism defining a center of rotation offset from that of a tibia bone axis,...http://www.google.es/patents/US6299646?utm_source=gb-gplus-sharePatente US6299646 - Knee prosthesis with a rotational plate
