Abstract: The present invention provides an articular endoskeletal prosthesis 1 for providing a user with at least one of a mechanically operable pivoting wrist, elbow and shoulder joint. The prosthesis 1 has at least one elongate endoskeletal tube upper limb member 5 with a proximal end portion 6 having a pivotal connection 7 to a support body 9 therefor. One of said upper limb member proximal end portion 6 and said support body 9 has a fixed worm gear wheel means 19 and the other a drive motor 22 having a drive output worm 25 extending generally tangentially of said worm gear wheel means 19 for engagement with the gear teeth of said worm gear wheel means 19 so that when said drive motor 22 is operated, in use of the prosthesis 1, said upper limb member 5 moves around said worm gear wheel means 19 so as to pivot said upper limb member about its pivotal connection 7.