What is shoulder arthritis?
Shoulder arthritis is a condition where the joints of the shoulder are inflamed and/or eroded. The term ‘shoulder arthritis’ is broad since it does not clearly indicate which of the two shoulder joints are affected or what type of arthritis afflicts the joint. It is often incorrectly used to describe other conditions affecting the shoulder like bursitis or adhesive capsulitis (frozen shoulder).
Joints of the Shoulder
The shoulder joint is not a single joint. There are actually two joints at the shoulder.
- Acromioclavicular (AC) joint is the smaller of the two. It is the point where the collarbone (clavicle) articulates with the acromion of the scapula (shoulder blade).
- Glenohumeral joint is the larger joint where the arm bone (humerus) articulates with the glenoid portion of the scapula (shoulder blade).
One or both joints may be affected in shoulder arthritis and the symptoms can vary slightly due to the differences in location.
Types of Shoulder Arthritis
There are various different types of arthritis that can affect any joint in the body, not only the shoulder joint. Osteoarthritis (OA) is the most common followed by rheumatoid arthritis (RA). Given the anatomy and function of the shoulder, post-traumatic arthritis is another common type.
- Osteoarthritis is a condition where the cartilage lining the bones of the joint becomes worn down. Over time the cartilage can crack and parts break off. Eventually the underlying bone is damaged.
- Rheumatoid arthritis is a condition where the lining of the joint known as the (synovium) is inflamed due to repeated irritation and attack by the immune system.
- Post-traumatic arthritis as the name suggests is arthritis that occurs after injury to the the joint. It can be injuries such as dislocation, fractures and torn rotator cuff (shoulder) muscles. This is a form of osteoarthritis.
Location of Shoulder Joints
The glenohumeral joint is located at the side of the very top of the arm. Arthritis of this joint is typically felt at the edge of the shoulder and more towards the back. The acromioclavicular (AC) is located in the front but towards the outer sides of the joint. Pain is therefore felt at the front when the AC joint is arthritic.
Signs and Symptoms
The symptoms may vary depending on the type of arthritis and the joint that is affected. However, the predominant symptom in all types of shoulder arthritis is pain and stiffness to some degree as well. Post-traumatic arthritis symptoms are largely the same as
Shoulder pain that is worse with movement in osteoarthritis, particularly with overuse of the joint as a result of arm movement. The pain tends to ease with rest. Rheumatoid arthritis is generally painful all of the time and movement and strain on the joint will worsen the pain.
The stiffness in rheumatoid arthritis is worse in the mornings and after periods of prolonged rest. It eases with movement and during the course of the day. Osteoarthritis stiffness is generally constant and worsens with time. Severe joint strain worsens the stiffness.
Redness and Swelling
Redness and swelling of the skin over the joint is more prominent in rheumatoid arthritis as it is an inflammatory condition. There may at times be some moderate swelling over the joint in osteoarthritis although this is largely absent. Bone spurs in osteoarthritis may be felt as hard protrusions under the skin.
The range of motion of the shoulder joint is typically reduced with arthritis. This is largely associated with stiffness and pain. A person may find it difficult to conduct otherwise simple tasks with the affected arm.
Abnormal joint sounds
A grating sound with movement, particular when the joint is experiencing strain, is a common symptom of osteoarthritis as the ends of the bone rub together. Other sounds that may be commonly heard includes a clicking or cracking of the joint especially when moving the arm to the limit of its hampered range of motion.
Causes and Risk Factors
Wear and tear on the joint cartilages are a normal part of everyday life. Sometime the forces on the joint are such that the cartilage gets worn out faster than normal. With age the cartilage’s ability to regenerate at a fast enough rate is hampered thereby allowing the cartilage to erode. Therefore osteoarthritis is a degenerative joint condition. Eventually pieces of cartilage break off into the joint space. The bones that it covers are exposed and rub against each other. The condition is more common in a person who uses the shoulder joint on a frequent basis or repeatedly strains the joint. It is a possible occupational hazard and also seen in professional sports people like baseball pitchers.
The exact cause of osteoarthritis is unclear. The immune system forms antibodies against parts of the joint lining and this directs immune cells to attack the tissue. This causes inflammation of the joint lining. Rheumatoid arthritis is associated with certain autoimmune diseases and is more frequent in people with a family history of the disease. The use of certain medication and abnormal immune response after a viral infection may also play a role in osteoarthritis.
Post-traumatic arthritis is essentially osteoarthritis that was preceded and caused by a prior injury to the bones and joint. This injury causes the cartilage to wear down. It is a result of direct injury to the cartilage as well as abnormal articulation as a result of injury that strains and erodes the cartilage. Fractures and dislocation of the joint are the main injuries that lead to post-traumatic arthritis. It is more frequently seen in military personnel, professional athletes particularly with contact sports, with falls and after motor vehicle accidents.
Tests for Diagnosis
A diagnosis of shoulder arthritis can be made by the presentation of the symptoms. It is further supported if the shoulder pain is relieved with an anesthetic injection. Diagnostic investigations may help confirm shoulder arthritis. An x-ray is one of the more commonly utilized diagnostic investigations but a CT scan and MRI may be better options. Ultrasound of the shoulder joint may also be conducted to diagnose arthritis. Blood tests may reveal elevated blood cells and rheumatoid factor.
Treatment of Shoulder Arthritis
The first approach to treating shoulder arthritis is conservative measures along with medication for symptomatic relief.
- The shoulder should be rested as much as possible.
- Physical therapy and joint support with strapping may be helpful.
- Hot and cold therapy as directed by a physical therapist may be helpful in controlling episodes of pain and swelling.
- Non-steroidal anti-inflammatory drugs (NSAIDs) are used for pain relief and easing inflammation.
These are general measures for all types of shoulder arthritis. Other drugs and supplements may be of use for specific types of arthritis.
- Osteoarthritis : Treatment options are limited beyond NSAIDs and analgesics (pain killers). Glucosamine and chondroitin are supplements which are widely touted to help with reducing cartilage degeneration and possibly restoring it.
- Rheumatoid arthritis : There are a larger number of treatment options including corticosteroids, other immunosuppressants and anti-rheumatic drugs. It is used in conjunction with NSAIDs.
Shoulder Arthritis Surgery
Depending on the severity of the condition, extent of joint damage and responsiveness to medication, surgery may be needed in the treatment of shoulder arthritis.
- Joint replacement (arthroplasty) is one of the popular forms of surgery for shoulder arthritis. There may be total joint replacement known as total shoulder arthroplasty. Sometimes just the head of the humerus (arm bone) is replaced which is known as hemiarthroplasty.
- Fusion of bones is not a favored procedure these days but is still conducted where indicated. Glenohumeral arthrodesis is a procedure where the head of the humerus is fused with the glenoid or acromion of the scapula. Resection arthroplasty is where the end of the collarbone is removed and scar tissue fuses the remaining portion to the acromion of the scapula.