Shoulder arthritis can affect either of the two joints in the shoulder complex. The first joint is called the acromioclavicular joint (AC joint). It is a joint between the clavicle (collar bone) and the acromion (roof of the shoulder). The AC joint moves a little when the shoulder moves and can be injured in a shoulder separation. The second joint is the glenohumeral joint (GH joint). This is the ball and socket joint which connects the top part of the arm (humerus) to the shoulder blade (scapula). This joint allows the shoulder to have a wide range of motion in all directions.
Two types of arthritis can be seen in the shoulder complex. The first type, Osteoarthritis (OA), is the typical "wear-and-tear" arthritis, which can present at any age but typically appears in later life. In some cases, OA can present after an injury or fracture to the shoulder and is called post-traumatic arthritis. The second type of arthritis is inflammatory arthritis. Rheumatoid arthritis (RA) is a common example. This arthritis affects patients at an earlier age. It typically affects multiple joints in the body (elbows, knees, etc.).
When arthritis affects the shoulder joint, the lining on one or both sides of the joint called cartilage starts to wear out. Cartilage is a very smooth surface which allows the joint to move with very little friction and no pain. When the cartilage disappears, the undersurface of the cartilage starts to rub against the opposite side of the joint. This leads to less smooth motion (crepitus) which can be felt or heard. Furthermore, this can cause significant pain with motion. As the pain becomes worse, it can interfere with sleep and activities of daily living (combing hair, reaching things above shoulder level).
There are four different modalities used in the management of arthritis.
Over the counter medication such as Ibuprofen, Aleve and prescription medications such as Celebrex and Mobic are non-steroidal anti-inflammatory medications which can prescribed to decrease the pain and inflammation in the shoulder. These medications have proven to be effective in decreasing pain and increasing the shoulder motion.
These injections are given in either the GH joint or the AC joint to decrease the inflammation in the arthritic joint. The steroid is usually mixed with a numbing medication which makes the injection less painful and helps confirm the diagnosis of arthritis. The steroid medication takes about 24-48 hours to start to work and may last up to 3-6 months.
Physical Therapy (PT)
PT is used to keep the joint flexible and the muscles surrounding the joint strong. It does not treat arthritis but keeps the joint moving more smoothly.
Surgical treatment of both joints in the shoulder is very effective in eliminating pain and restoring function to the shoulder complex.
AC Joint Surgery
When the AC joint gets arthritic and does not respond to any of the above modalities, a distal clavicle resection can be performed with arthroscopy. This involves an outpatient procedure when three small incisions (about ¼") are placed around the shoulder. Both sides of the AC joint are excised to prevent the arthritic edges of the joint from rubbing against each other.
GH Joint Surgery
Surgery is used as a last resort when the above modalities fail and the patient cannot tolerate the pain and disability they feel anymore. In some very early stages of arthritis, an arthroscopy can be performed to debride, or "clean up" the shoulder. This means taking out the loose bodies in the shoulder, removing some of the inflamed tissue (synovium) and debriding the loose injured cartilage. In more advanced stages of arthritis, the shoulder joint can be replaced with a metal prosthesis. Check the section on shoulder replacement for more information.
Further information on this injury can be found in this article on the AAOS OrthoInfo website, an orthopaedic resource center providing expert information.