Abstract: A knee-jount endoprosthesis including a femoral part (2), a meniscus element (6) and a tibial part (12), the femoral part (2) and the tibial part (12) lying with their bearing surfaces in contact with associated bearing surfaces of the meniscus element (6). This endoprosthesis is capable of achieving the physiological knee-joint functions of movement and load-bearing while preventing local peak stresses, especially those caused by line or point contact. The femoral part (2) is provided with a spherical bearing surface (4) which lies on a corresponding spherical and concentrically disposed bearing surface (8) of the meniscus element (6). The tibial part (12) has a convex configuration and a cylindrical bearing surface which contacts a mating, coaxially arranged second bearing surface (10) on the meniscus element (6).