In a knee endoprosthesis comprising a tibia part, a femur part having two condylar surfaces, and a meniscus part arranged between the femur part and the tibia part, the meniscus part having on its upper side two bearing shells for receiving and mounting the condylar surfaces of the femur part and having on its underside a meniscus-bearing surface which rests in a displaceable manner on a tibia-bearing surface on the upper side of the tibia part, in order to allow as large a bending angle as possible, with best possible adaptation to the anatomy of the natural knee joint, it is proposed that the meniscus-bearing surface and the tibia-bearing surface each have a spherical projection or a spherical recess offset in a medial or a lateral direction in relation to their center, that the spherical projection on one of the two bearing surfaces engage the spherical recess of the other bearing surface and thereby form a ball bearing-like mounting of the meniscus part on the tibia part, and that in the lateral or medial part of the two bearing surfaces, these bearing surfaces form supporting areas bearing on each other, which are curved in a dorsal-ventral direction and have a radius of curvature there, which is greater than the radius of curvature of the spherical projection and the spherical recess by at least the factor 2.5.
