Abstract: A knee joint prosthesis (1) comprises a tibia part (1) having a tibia bearing surface (10) and a bearing body (3) which is slidingly displaceably journalled on the tibia bearing surface (10) and which has bearing scallops (31) on its side which is remote from the tibia bearing surface (10). Furthermore, it comprises a femur part (5) which is movably arranged on the bearing scallops (31) of the bearing body (3) as well as comprising a guide piece (2) which is arranged to be rotationally fixed relative to the tibia part (1) and which permits only a displacement of the bearing body (3) in the sagittal direction relative to the tibia bearing surface (1). Furthermore, it comprises a coupling member which cooperates both with the guide piece (2) and with the femur part (5) and permits a rotation of the femur part (5) on the bearing body (3).