Abstract: An artificial hip joint between a femur and a pelvis having increased rotational clearance on an internal side of the joint, including an acetabular cup for anchoring to the pelvis. The hip joint includes a femoral prosthesis having an elongated stem for anchoring to the femur with an upper end. A collar extends outwardly from the upper end and terminates in an end part opposite the upper end of the stem. A head portion is supported on the end part and pivotally mounted within the acetabular cup. The head and the end part have a common central axis. The collar includes a surface on the internal side that contacts the acetabular cup. The surface is offset from the common central axis in a direction away from the internal side so that the acetabular cup has increased rotational clearance on the interior side.