Shoulder arthritis is a condition that damages the cartilage inside the shoulder joint. The shoulder has two joints. Shoulder arthritis usually refers to the larger ball-and-socket joint, called the glenohumeral joint, after the bones it connects (the glenoid and the humerus). Cartilage covers both the ball-and-socket (head of the humerus) and the glenoid (the socket).
When the cartilage in the shoulder begins to degenerate on the surface and eventually in the deeper layers, the condition is called shoulder arthritis. The second joint in the shoulder, the acromioclavicular joint or AC joint, can also become inflamed, which is called AC arthritis.
Causes and Types of Shoulder Arthritis
There are many different types of shoulder arthritis. Each type may have a different origin, and some causes of shoulder arthritis are unknown.
- Shoulder Osteoarthritis: Osteoarthritis is also known as degenerative joint disease. It is often associated with wear and tear due to aging. In addition to the shoulder, osteoarthritis can also affect other joints and is the most common form of arthritis.
- Rheumatoid Arthritis in the Shoulder: Rheumatoid arthritis is an autoimmune disease, meaning your body attacks your own healthy cells, including the lining of your joints. This arthritis can occur in both shoulders at the same time.
- Post-traumatic arthritis of the shoulder: If your shoulder is broken, dislocated, or injured, you may develop post-traumatic arthritis.
- Rotator cuff tear arthritis: Rotator cuff tear arthritis is a type of shoulder arthritis that can develop after a large, long-lasting tear in the rotator cuff. The four rotator cuff tendons in the shoulder wrap around the head of the shoulder bone, holding the shoulder joint in place. If one or more of these tendons are severely torn, the head of the humerus can rub against other bones and lead to arthritis.
- Avascular Necrosis of the Shoulder: Avascular necrosis is a condition in which the blood supply to an area of the body is interrupted, causing the area to die (necrosis). In the shoulder, the head of the humerus (the ball of the shoulder joint) can lose its blood supply due to disease, injury, and other causes. Without blood supply, the bone gradually collapses, becomes uneven, and causes arthritis.
Symptoms of Shoulder Arthritis
The degree of cartilage loss varies from person to person, and the symptoms of shoulder arthritis vary as well:
1. Shoulder pain is the main sign of arthritis
Pain may occur in the front, side, or back of the shoulder. Some people have pain even when not using the arm, and some people only have pain when using it. Arthritis pain can occur at any time of the day and may or may not be accompanied by stiffness. The pain is often worse when lifting, carrying heavy objects, or after exercise. The pain may often radiate down the arm or, if severe, down to the elbow and wrist.
2. Stiffness
Stiffness is another sign of advanced shoulder arthritis. You may experience stiffness due to a loss of range of motion in your shoulder. As your range of motion decreases, you may find that your arm does less, and these activities may be limited by pain.
3. Grinding, clicking, or popping (crepitus)
Grinding, clicking, or popping may occur due to uneven cartilage surfaces caused by arthritis. This may or may not be painful. Sometimes the shoulder may “lock up.” Sometimes, because the cartilage surfaces are no longer smooth, you may feel like your shoulder is slipping in certain positions.
