Like any joint, the shoulder can be the site of osteoarthritis, that is to say a degradation of the cartilage. This is called omarthrosis or osteoarthritis of the shoulder. This can be qualified as centered or eccentric depending on whether the tendons of the cuff which fit around the shoulder are preserved or not. The treatment is first-line medical and aims to relieve pain. When the pain and functional discomfort become disabling, it is recommended to replace the joint with a shoulder prosthesis.

Osteoarthritis is the term used to speak of osteoarthritis of the glenohumeral joint or osteoarthritis of the shoulder. This is a more common pathology in patients over 50, which results in progressive destruction of the cartilage in the shoulder.

Osteoarthritis can be centered or eccentric:

• Centered osteoarthritis results in progressive wear and tear of the joint, but the tendons of the cuff which insert around the shoulder are preserved. Although this form of osteoarthritis results in a stiff and painful joint, it leaves a normal shoulder mobility capacity. It is more common in women and in patients whose professional activity results in overuse of their shoulder; 
• Eccentric osteoarthritis, on the other hand, is characterized by a damaged joint and an old and massive rupture of the tendons of the cuff that insert around the shoulder. The head of the humerus is off-center with respect to the glenoid of the scapula, and becomes eccentric. As the motor muscles are no longer in place, the shoulder no longer has normal mobile capacities.

The articular cartilage, which surrounds our bones, is a “living” tissue, which is constantly renewed. Omarthrosis occurs when this phenomenon is disturbed and the cartilage is destroyed more quickly than it is rebuilt. As the function of this protective layer is to provide painless sliding of the joint surfaces allowing movement of the shoulder, cartilage degeneration leads to painful friction between the bones and the formation of bone growths, called osteophytes. During cartilage destruction, small pieces of cartilage can also detach and “float” in the joint pocket: they then trigger mechanical inflammatory outbreaks which result in hypersecretion of fluid and swelling of the joint, also called hydarthrosis.

Centered osteoarthritis can be the natural consequence of the aging of the joint or follow a trauma such as a fracture, a sprain, a recurrent dislocation or an infection. It may also not have a specific cause. In 40% of cases, this form of osteoarthritis affects both shoulders. It is then said to be bilateral.

Osteoarthritis causes bone growths as well as pain that limits the mobility of the shoulder.

Whether the osteoarthritis is centered or eccentric, the pains first appear on exertion, when the joint is requested, to quickly become almost permanent and lead to discomfort in daily movements, up to disrupting the patient’s sleep. Shoulder crunches, blockages as well as inflammatory or mechanical pain occur. This results in a handicap in the activities of daily living, a source of great functional discomfort.

When osteoarthritis is centered, it is characterized by very frequent joint stiffness and almost constant pain. When it is off-center, pain and significant functional discomfort are present because the shoulder has lost its normal mobile capabilities.

It is primarily a matter of relieving pain by resorting to:

• resting;
• rehabilitation sessions;
• analgesics;
• anti-inflammatory drugs during hyperalgesic phases, that is to say peaks of extreme pain;
• synovial fluid infiltration, or visco-supplementation, in the joint.

The above measures provide pain relief for a period of time but do not slow down the progression of the disease. Over time, these can become ineffective and no longer provide lasting relief to the patient.

When the pain and functional discomfort become disabling, it is recommended to replace the joint with a prosthesis. Surgery involves replacing worn joint surfaces with prosthetic implants, in order to reduce painful friction and restore mobility to the joint. There are two types of shoulder prostheses:

• total anatomical prostheses, which have two parts that reproduce the anatomy of the humerus and the scapula, and which are used when the tendons that mobilize the shoulder are still present and not too damaged; 84% of anatomical shoulder prostheses are still in place after 20 years;
• reverse total prostheses, which have the particularity of having their own stability allowing them to function despite a rupture of the tendons and muscles of the rotator cuff; 91% of reverse shoulder prostheses are in place after 10 years.

The resumption of routine activities is usually carried out from the second or third month, following the surgery. The final result is observed after 1 year.