Osteoarthritis is the most common type of arthritis in the shoulder. Less commonly seen types of arthritis in the shoulder are rheumatoid arthritis (inflammatory) and arthritis that can occur after shoulder trauma.
In osteoarthritis, the smooth cartilage that covers the ends of the bones gets worn away, causing the rough bone ends to rub against each other. This leads to irregular motion within the joint and to the development of bone spurs (osteophytes), which are bony growths formed as the bone tries to heal itself. Irregular motion and bone spurs along with inflammation can result in pain and loss of motion in the shoulder.
The most common complaint of someone with shoulder arthritis is the pain. The pain worsens with activities, especially with any activities that require the arms to reach over the head, and decreases with rest. The next most common complaint is loss of motion. In addition, the motion of the shoulder can sometimes feel like grinding (also known as crepitus) as the bones rub on one another.