Abstract: A total elbow replacement prosthesis for dogs is provided. A humeral component has an elongated stem carried by the humerus and a generally cylindrical head carried by the stem. The cylindrical head has a spiral groove formed at an angle substantially the same as the angle of the trochlear notch in a healthy ulna. A radial ulnar component is provided having a body and a formed plastic seat against which the head of the humeral component sits and articulates. The plastic seat includes a vertical ridge which engages the spiral groove to provide lateral support for the prosthesis and to mimic the natural motion of a healthy elbow. The radial ulnar component is anchored to the ulnar. A radial cap is carried by the proximal end of the radius and has a domed surface adapted to engage a recess in the body of the radial ulna component.