Osteoarthritis is the most common type of shoulder arthritis. Also called wear-and-tear arthritis or degenerative joint disease, osteoarthritis is characterized by progressive wearing away of the cartilage of the joint. As the protective cartilage is worn away by shoulder arthritis, bare bone is exposed within the joint.
The other type of shoulder arthritis that is not uncommon is rheumatoid arthritis. Rheumatoid arthritis is a systemic condition that causes an inflammation of the lining of a joint. This inflammation can, over time, invade and destroy the cartilage and bone.