Old senior man with shoulder pain

Why Have I Developed Shoulder Arthritis?

Shoulder osteoarthritis is a painful condition which can affect any of the joints making up the shoulder girdle. Eventually it results in the wearing away of the cartilage in the joint.

The shoulder girdle contains three joints. One is the glenohumeral joint which connects the glenoid (or shoulder socket) and the humerus (the upper arm bone which ends in the humeral head or ball). The others are related to the collarbone (clavicle);the sternoclavicular or SC joint is where the clavicle meets the breastbone (sternum) and the acromioclavicular or AC jointis where the clavicle meets a part of the shoulder blade called the acromion.

Arthritis most commonly affects either the larger glenohumeral joint or the smaller AC joint both. It can be primary, where the cause is due to a mechanical problem in the joint leading to excessive ‘wear and tear’, or secondary to another problem such as a severe injury.

Types of arthritis and what causes them

Shoulder arthritis diagramPrimary osteoarthritis: Thanks to researchers in Switzerland, we know now that the most cases of primary glenohumeral osteoarthritis is due to subtle variations in the shape of the shoulder bones which affects the biomechanics of how the joint functions.

Over the course of many years these slight differences result in the large shoulder muscles putting excess strain on the cartilage of the joint.The cartilage in the joint starts to break down, causing the bones to begin rubbing together. The bone surface expands to reduce the pressure, producing spurs of bone called osteophytes.

Eventually small cracks develop in the surface of the bone through which joint fluids leaks into the bone causing bone cysts. The age at which a person develops arthritis is dependent on how much their bone structure differs from the average; the more the variation the sooner they will develop osteoarthritis.

The biomechanical reasons for primary AC Joint arthritis are less well defined, but it is much more common in men who do manual work or a lot of heavy overhead lifting. It is due to damage to the cartilage in the AC joint where the collarbone (clavicle) and shoulder blade (scapula) meet. As the cartilage wears down, the bones can no longer move smoothly against each other and they may start to rub. Bony spurs and cysts form around the joint. Read about AC injuries here. 

Secondary osteoarthritis: This is where the breakdown of cartilage in the joint has been caused by a defined and identifiable reason. One reason is inflammatory arthritis, of which the most common form is rheumatoid arthritis. This is an unfortunate disorder where elements in the bloodstream deposit in joints and attack the lining of the joint. The intense inflammation results in cartilage damage and osteoarthritis. It tends to affect both shoulders symmetrically with a generally normal biomechanical bone structure. Sometimes shoulder arthritis is the first presentation of inflammatory arthritis. It is important for a doctor to recognise this as further treatment may be available from a Rheumatologist to prevent the  same happening to the other joints in the body.

Another common cause is rotator cuff tear arthropathy. The rotator cuff is a group of four tendons and muscles that keep the shoulder stable within its socket. In some patients if a rotator cuff tear is left untreated for a long time  the shoulder joint becomes extremely unbalanced and causes excessive wear to the cartilage at the top of the joint, resulting in osteoarthritis. Read about the causes of rotator cuff tears and what you can do about it here.

Avascular Necrosis is caused by disruption to the blood supply of the humeral head which may be due to disease, injury or other causes. Loss of blood supply causes the bone supporting the cartilage to die resulting in an irregular joint surface resulting in wearing away of the cartilage. It has a long list of causes but the most common is a severe fracture affecting the ball of the humerus. Equally, even if avascular necrosis does not occur, if the fracture does not heal in a smooth anatomical way then post-traumatic osteoarthritis can occur for the same reason.

Symptoms of shoulder arthritis

Although the type of shoulder arthritis varies, the symptoms are similar although they can differ in severity depending how advanced the condition is. Common symptoms include:

  • Pain in the front, side or back of the shoulder which can sometimes extend to the neck, elbow, wrist and hand. The pain is often worse at night and the shoulder may become increasingly weak. Carrying heavy objects or exercising can exacerbate it.
  • Stiffness in the shoulder joint which may reduce the joint’s natural movement and function.
  • Crepitus, which is a sensation of grinding, clicking or cracking. The shoulder can sometimes lock up.

What to do about shoulder arthritis

If you are experiencing any of these symptoms it is important to get a proper diagnosis. Although there is no cure for arthritis, there are treatments that might help to slow the development of the disease or ease the symptoms. However, surgery may be the only way to treat more advanced arthritis.

Non-surgical treatments for less advanced arthritis include exercises to increase movement and flexibility, painkilling medication and lifestyle changes. You may also be able to have an injection into your shoulder to reduce pain and inflammation.

If you have been diagnosed with a rotator cuff injury or you have symptoms that suggest you might have torn your rotator cuff, contact us to discuss your diagnosis and the treatment options most suitable for you.