Shoulder osteoarthritis, also known as degenerative bone disease and commonly called arthritis, is a disorder in which cartilage, which acts as a protective cover for the bones, degenerates. Without cartilage to act as a buffer, the affected bones rub together and wear each other down, resulting in pain and swelling.
Sometimes bone spurs, which are also painful and interfere with movement, develop from the friction created by the bones' rubbing together. Other medical conditions, such as bursitis, an inflammation of fluid-filled sacs called bursae, or rheumatoid arthritis (RA), an autoimmune disorder, may present with symptoms similar to those of osteoarthritis.
Anatomy of the Shoulder
The shoulder is made up of three bones: the humerus (upper arm bone), the scapula (shoulder bone) and the clavicle (collar bone). There are two joints where these bones connect: the acromioclavicular (AC) joint, where the collarbone attaches to the tip of the shoulder blade, and the glenohumeral joint, where the top of the arm bone connects to the shoulder blade. Osteoarthritis most commonly occurs in the AC joint.
Causes of Shoulder Osteoarthritis
There are two types of osteoarthritis of the shoulder: primary and secondary. They are differentiated by their causes.
Primary Shoulder Osteoarthritis
Primary osteoarthritis is the result of normal aging. Over the years, as stress is put on the joints, cartilage wears thin and sometimes even erodes completely, resulting in stiffness and pain. Primary osteoarthritis is much more common in certain families, and clearly has a genetic component.
Secondary Shoulder Osteoarthritis
Secondary osteoarthritis is the result of another issue or medical condition. Osteoarthritis of the shoulder can be caused or exacerbated by the following:
- Congenital abnormalities
- Traumatic injury
- Repeated stress or trauma (as from playing sports)
- Autoimmune disease
- High-dose corticosteroid usage
- Repeated surgery to joints
- Endocrinological diseases
A serious type of secondary osteoarthritis of the shoulder, known as avascular necrosis, occurs when the blood supply to the humerus is interrupted. Avascular necrosis can cause the death (necrosis) of bone cells in the shoulder, which eventually results in osteoarthritis. In addition to occurring post-injury, avascular necrosis can be caused by alcoholism or heavy use of steroids.
Symptoms of Shoulder Osteoarthritis
There are three major symptoms of osteoarthritis of the shoulder. They are the same symptoms common to osteoarthritis affecting other parts of the body.
The predominant symptom of osteoarthritis is pain that is aggravated by active or passive movement, and which becomes increasingly severe. As the osteoarthritis progresses, patients may experience pain intense enough that it interferes with sleep.
Limited Range of Motion
When attempting to move the arm, whether during normal activity or a physical examination, a patient may be unable to reach, turn or stretch the arm to the usual extent.
Abnormal Joint Sound
The patient's shoulder may produce a clicking, snapping or grinding sound called crepitus, which results from the bones at the affected joint making contact with one another.
Diagnosis of Shoulder Osteoarthritis
In order to diagnose osteoarthritis of the shoulder, a thorough physical examination is performed to evaluate pain level, muscle weakness, range of motion, and any possible involvement of other joints. A complete medical history that assesses family history and past injuries is taken. If the physical examination indicates shoulder osteoarthritis, other diagnostic tests may be performed, including:
- MRI scan
- Blood tests to screen for other diseases
- Analysis of fluid that lubricates the joint
Treatment of Shoulder Osteoarthritis
Although there is no known way to regenerate cartilage, several treatments are effective in reducing pain and increasing range of motion. They include altering daily activities to rest the shoulder joint; applying moist heat or ice; taking over-the-counter nonsteroidal anti-inflammatory drugs (NSAIDs); and engaging in prescribed physical therapy. Other medications may also be prescribed. Although the research is inconclusive, many patients say that taking the dietary supplements glucosamine and chondroitin is helpful in relieving symptoms of osteoarthritis of the shoulder.