Patent ID: 8246688

Claim:
Knee endoprosthesis comprising: a tibia part having on an upper side a tibia-bearing surface; a femur part having two condylar surfaces; and a meniscus part arranged between said femur part and said tibia part; said meniscus part having on an upper side two bearing shells for receiving and mounting the condylar surfaces of said femur part and having on an underside a meniscus-bearing surface which rests in a displaceable manner on the tibia-bearing surface; said meniscus-bearing surface comprising one of a spherical projection or a spherical recess offset in one of a medial or a lateral direction in relation to a center of the meniscus-bearing surface; and said tibia-bearing surface comprising the other of the spherical projection or the spherical recess offset in the corresponding medial or lateral direction of the tibia-bearing surface, such that the spherical projection on one of said two bearing surfaces engages the spherical recess of the other bearing surface and thereby forms a ball bearing-like mounting of said meniscus part on said tibia part which is offset in the corresponding medial or lateral direction of the bearing surfaces; and wherein: in the other of the lateral or medial direction of said two bearing surfaces, the two bearing surfaces each form corresponding supporting areas which bear on each other, the supporting areas are correspondingly curved in a dorsal-ventral direction and have a radius of curvature which is greater than a radius of curvature of said spherical projection and said spherical recess by at least the factor 2.5, the supporting areas of the two bearing surfaces are also curved in a lateral-medial direction, and the supporting areas extend along one or more lines, which result as lines of intersection of two cylinder surfaces, namely a perpendicular cylinder surface having a center axis which passes through a center point of the spherical projection and the spherical recess and extends substantially parallel to a tibial longitudinal axis, and a horizontal cylinder surface having a center axis which passes through a center point defined by the curvature extending in the dorsal-ventral direction and extends substantially in a medial-lateral direction.