Abstract: A hip prosthesis comprising a first fastening assembly (1, 2, 6, 12, 13) intended for being mounted in the hip bone (A) and a second fastening assembly (4, 5, 7, 14) intended for being mounted in the upper extremity of the femur (F), wherein the first (1, 2, 6, 12, 13) and the second (4, 5, 7, 14) fastening assemblies are interconnected by means of a pivotable connection (8, 108) wherein all parts (1, 2, 4, 5, 6, 7, 8) of the hip prosthesis are so small and/or slender that they can each be arranged in the intended end position thereof via a bore (9) in the femur (F), which bore (9) extends from the outside (Fo) of the femur (F) through the femoral neck (Fn) substantially in the direction of the imaginary longitudinal center line (LFn) of the femoral neck (Fn) to the femoral head (Fh)