A hip/shoulder prosthesis includes: a head component; a metaphyseal component; a diaphyseal nail, and a locking device. The head component includes: a front face and rear face; with a bore, and first and second shaped recesses in the rear face. The metaphyseal component includes: a central transverse aperture at an angle to the metaphyseal component's axis; a first end configured for threaded engagement within the bore of the head component; and a longitudinal hole that begins at the second end, transects the transverse aperture and reaches the first end, to receive the locking device. The diaphyseal nail is inserted in the femoral or humeral canal, and includes: fastening apertures that receive corresponding screws for fastening the diaphyseal nail to the femur or humerus; a portion configured to he received within, and engage, the transverse aperture of the metaphyseal component, and a transverse hole configured to receive the locking device.