In the shoulder, the different joints, and particularly the scapulohumeral (or glenohumeral) joint, which is located between the joint heads of the scapula and humerus, are normally lined with cartilage, which allows them to avoid the friction that would otherwise be created during movements.
In shoulder osteoarthritis, the cartilage wears down causing pain and stiffness; this occurs in predisposed individuals and generally in old age.
The condition is progressive in nature, eventually leading to severe limitation of daily activities for the sufferer.
The thinning of cartilage, over time, also goes on to affect the head of the humerus and glenoid cavity, developing callosities, growths and holes.
In more advanced stages, the synovial membrane, which lines the joint, may also be compromised and become inflamed, increasing synovial fluid production resulting in swelling.
In contrast to hip and knee osteoarthritis, shoulder osteoarthritis is quite rare.
