This invention relates to a joint prosthesis. The joint prosthesis has an anchoring means (1, 51, 100) arranged to be placed in a bone to rest against and be supported by an inside surface of the cortical bone layer. The anchoring means (1, 51, 100) may be placed in a bore along an extra medullary axis of a bone, such as the femur (F), and be supported by the cortical bone layer distal from the hip joint. Locking means (2, 2', 3, 3', 52, 106) are provided in order that the anchoring means (1, 51, 100) can be inserted through an inlet opening (Fi) and be supported by the inside surface (C) of the cortical bone wall adjacent the opening (Fi).