In accordance with the invention a knee joint endoprosthesis comprises a femoral component and a meniscal component mounted for movement relative to and on said femoral component. Said femoral component comprises a medial and a lateral condyle having a medial and a lateral condylar surface. Said meniscal component comprises a medial and a lateral joint surface on which the medial and lateral condylar surfaces bear at least partially. Said medial condyle and said medial joint surface are shaped so as to form a rotary joint with a rotary joint center. Moreover, a rolling motion guiding device is provided for defined rolling of the lateral condylar surface and the lateral joint surface on each other along a curved path which is defined in dependence upon an angle of flexion between femoral component and meniscal component and extends around the rotary joint center.
