This surgery alleviates pain by replacing the damaged bone and cartilage with a metal and plastic implant. The shoulder joint is a ball-and-socket joint, much like the hip joint. The ball is the top of the arm bone (the humerus), and the socket is within the shoulder blade (scapula).

When shoulder replacement surgery is performed, the ball is removed from the top of the humerus and replaced with a metal implant. This is shaped like a half-moon and attached to a stem inserted down the center of the arm bone. The socket portion of the joint is shaved clean and replaced with a plastic socket that is cemented into the scapula.