When shoulder pain stemming from arthritis, degenerative joint disease, or traumatic injury cannot be alleviated by conservative treatments, shoulder replacement (or shoulder arthroplasty) can successfully restore comfort, as well as improve range of motion, function, and strength. The well-established surgical procedure involves replacing both the ball (humeral head) and socket (glenoid bone) of the shoulder joint with manufactured components made of either plastic or metal. The ball replacement contains a stem that attaches it to the arm bone (humerus), and the socket replacement is held in place with special cement. Patients undergoing shoulder replacement typically are in the hospital for two to three days, and begin rehabilitation on the day of surgery.