The shoulder is a highly movable body joint that allows various movements of the arm. It is a ball and socket joint, where the head of the humerus (upper arm bone) articulates with the socket of the scapula (shoulder blade) called the glenoid. The two articulating surfaces of the bones are covered with cartilage, which prevents friction between the moving bones.
The cartilage is lubricated by synovial fluid. Tendons and ligaments around the shoulder joint provide strength and stability to the joint. When the cartilage is damaged, the two bones rub against each other resulting in pain, swelling and stiffness of the joint (osteoarthritis).
Total shoulder replacement surgery is performed to relieve these symptoms. In this surgery, the damaged articulating parts of the shoulder joint are removed and replaced with artificial prostheses. Replacement of both the humeral head and the socket is called a total shoulder replacement.