Patent ID: 8491661

Claim:
A knee joint endoprosthesis, comprising: a femur component and a tibia component, which comprise cooperating joint surfaces that are in contact with one another, a rotation guide arrangement for forcing a rotational movement of the femur component and the tibia component relative to each other about a medial center of rotation due to a flexure of the knee joint endoprosthesis, which rotation guide arrangement comprises a first guide element having a first guidance surface and a second guide element having a second guidance surface which cooperates with the first guidance surface, wherein: the tibia component comprises the first guide element, the femur component comprises the second guide element, the first guidance surface defines a first radius of curvature, the second guidance surface defines a second radius of curvature, and the first and second radii of curvature are identical, the first and the second guidance surfaces abut against each other along an even circular arc section within a flexion angle range which is defined by a minimum and a maximum flexion angle, and at least one of roll upon one another and slide upon one another during a flexural movement, the femur component comprises two joint surfaces which are configured to be mirror-symmetrical with respect to a second mirror plane running substantially in the anterior-posterior direction, the second guidance surface is configured such that a center point is defined for each flexion angle when there is a flexion of the knee joint endoprosthesis with a flexion angle within the flexion angle range of the circular arc section, and the center points lie on a center point plane which runs parallel to the second mirror plane but offset in a lateral direction.