Abstract: The invention relates to knee joint endoprosthesis consisting of a femur part provided with two skid surfaces leaving a free space between each other, said surfaces being connected with each other in front and having their curvature increasing from the front towards the rear and being curved also on planes perpendicular to said curvature; a tibia part having two surfaces on which the skid surfaces ride in a sliding manner, with an elevation being disposed between said two surfaces; and of artificial connecting means for keeping the two parts of the prosthesis together.