Arthritis is damage to the cartilage in a joint. Similar to arthritis of the knee and hip joints, shoulder arthritis occurs when the cartilage starts wearing down on the ball and/or socket sides of the shoulder joint. 

According to the Center for Disease Control and Prevention (CDC), an estimated 50 million adults in the United Statesreported being told by their physicians that they have some form of arthritis (osteoarthritis, rheumatoid arthritis, post-traumatic arthritis, etc). This number means ~ 1 in 5 adults (22%) in the U.S.A. have the diagnosis of arthritis, and in 2007-2009, 50% of adults over the age of 65 years have been diagnosed with arthritis. Nearly 1 in 2 people may develop symptomatic knee arthritis by the age of 85 and 1 in 4 people may develop painful hip arthritis in their lifetime. In 2004, there were 454,652 total knee replacements, 232,857 total hip replacements, and 41,934 total shoulder replacements done in the U.S. The number of total shoulder replacements is projected to increase from its current rate up to 322% by the year 2015. The relatively lower number of total shoulders performed when compared to the total knee and hip procedures maybe due to the ability of patients to tolerate shoulder arthritis much longer than hip or knee arthritis as the shoulder is not a weight-bearing joint. Usually, patients come see the orthopaedic surgeon when pain limits sleep and function affects their quality of life.There are three major types of arthritis including osteoarthritis, rheumatoid arthritis, and post-traumatic arthritis of the shoulder.1) Osteoarthritis of the shoulder is a disease that involves breakdown of the articular cartilage that normally allows the joint to glide smoothly with each other. Loss of cartilage is seen on xray as loss of the joint space. Cartilage breakdown may be caused by wear and tear over time, but the key point is that cartilage does not heal when damaged. Instead, the body tries to heal by making more bone and this results in an irregular joint with extra bone spurs called osteophytes. The result is loss of motion due to irregular joint surfaces. In addition, the inflammation caused by the arthritis results in thickening and scarring of the joint capsule which also contributes to loss of motion.

2) Post-traumatic arthritis of the shoulder results when the shoulder joint is injured. This can be a result of bone fracture, dislocation, or damage to the surrounding ligaments/soft tissue around the shoulder joint. This is a 22-year-old woman with arthritis after a fracture skiing and a surgical repair (screws and plate have been removed). Note that the humeral head (ball) is irregular and flattened.

3) Rheumatoid Arthritis and other inflammatory conditions of the shoulder is a systemic disease that can affect any joint in the body. This is a condition in which the lining of the joint (synovial cells) develops inflammation which damages the cartilage and bone of the shoulder. In some cases it is inherited and a family history of rheumatoid arthritis may be a cause. Women are affected more frequently than men and sometimes young adults can develop a form of this called juvenile rheumatoid arthritis. Typically, other joints are also affected such as the hands, knees, and even the spine.Your physician may order blood tests which show markers for this inflammatory condition. This condition is different than typical osteoarthritis, as the process often results in erosions of the bone around the joint, and the rotator cuff tendons may also be damaged. In some cases, bony erosions and tendon damage may be severe. The lower image shows a severe loss of tendons and erosion of bone that has caused the humeral head to move upward out of the socket.

Other Causes: Arthritis can occur after surgery as when anchors for an instability repair are placed in a location to damage the joint cartilage. The patient’s XRays below shows anchors placed in a location that damaged the joint cartilage. This patient developed arthritis as the result of metal anchors placed into the joint surface during a surgery to treat recurrent shoulder instability. The joint is irregular and there are erosions of the glenoid (socket).