Mono-condylar knee joint prosthesis

A, mono-condylar knee joint prosthesis comprising a femur part having a convex running surface, a tibia part having a planar sliding surface which faces the femur part, and an intermediate part which is introduced between the femur part and the tibia part during implantation, said intermediate part having a first, concave bearing surface for cooperating with the convex running surface of the femur part and a second, planar bearing surface for cooperating with the sliding surface of the tibia part such that the intermediate part is slidingly displaceable on the sliding surface of the tibia part, wherein a boundary surface is provided at the tibia part on an inner side of the tibia part which bounds the sliding surface of the tibia part and projects in a direction towards the femur part in order to cooperate with a side surface of the intermediate part, wherein the boundary surface which is provided at the tibia part is curved in the shape of an arch;

• wherein the intermediate part has a side surface which is curved corresponding to the boundary surface which is provided at the tibia part and which is curved in the shape of an arch, wherein the boundary surface which is provided at the tibia part is curved in the shape of a convex circular segment and the side surface of the intermediate part is correspondingly curved in the shape of a concave circular segment, wherein the concave bearing surface of the intermediate part and the corresponding running surface of the femur part are each designed in the shape of a spherical segment, and wherein the side surface of the intermediate part extends over an angle of arc that lies in a range of 24 degrees to 45 degrees.