Abstract: A modular prosthesis has an intramedullary rod element which is to be inserted in a bone. The rod has a shaped proximal portion which is telescoped into one end of a bore in the trochanter element. The mating surfaces of the shaped rod and the trochanter bore form a rotationally immovable connection. A neck element is telescoped into the other end of the trochanter bore. The neck and the trochanter have mating surfaces with mating recesses. A key lock element is inserted into the mating recesses to prevent rotational movement between the neck and the trochanter. All the elements are secured together by a bolt through the neck, trochanter and rod.