The tendons are the gristle that join muscles to bone
At the shoulder, these tendons run in a narrow space between the top of the arm bone (the humerus) and the underside of the shoulder blade. You can see the arrangement in this picture.
If the tendons become swollen due to inflammation or injury then there is no longer enough room for them to move freely and they rub against (or impinge themselves) against the bone above.
Likewise, shoulder impingement can occur if the bone around the shoulder develops wear and tear changes and thus becomes thicker and rougher. This also triggers an impingment reaction.
In most cases a mixture of the two scenarios above is the cause of the shoulder impingement syndrome that develops.
The longer term effect of the shoulder impingement process can be to cause further weakening of the tendons - worsening impingement - further weakening of the tendons ... and so on in a viscious circle.
The constant rubbing effect of tendon on bone can result in the tendons themselves becoming worn or degenerate. This can make surgical treatment of the shoulder impingement syndrome more difficult.
What causes Shoulder Impingement Syndrome
Impingement syndrome at the shoulder is usually the end result of an inflammation reaction. The initial inflammation reaction usually arises after an injury such as a fall or as a result of unaccustomed overuse of the shoulder joint or shoulder muscles.
Sometimes the sufferer will not be able to recall a specific trigger and it can seem as if the initial pain just starts out of no where.
The tendons of the shoulder become inflamed and swollen - starting the shoulder impingement process. Over months or years the patient will experience intermittent pain.
Gradually the tendons become worn to the extent that they fail to move the shoulder in a fully controlled way. This creates friction against the nearby bone and triggers wear and tear changes in the bone - making the shoulder impingement worse. The process continues until the patient experiences more or less constant ache in the shoulder with more severe pain on overhead activities.
Bursitis can exist on its own or in association with inflammation of the shoulder tendons. Shoulder tendon inflammation is called tendonitis
How to diagnose Shoulder Impingement Syndrome
The symptoms of shoulder impingement syndrome often begin gradually over some weeks or months. Pain is the main problem. Rarely the problem can start with severe pain and progress rapidly but this is not common. More often it starts with a gradual pain in the region of the outer part of the shoulder - over the deltoid muscle. Having problems trying to sleep on the affected side is a common symptom
The pain of an impingement syndrome is felt over the deltoid muscle area around the shoulder. It may spread down the arm towards the elbow or wrist. The impingement pain is made worse by lying on the affected side or by trying to use the arm above the head.
Some people become aware of a "painful arc" of movement. This means that they have no pain when their arm hangs by their side but they develop a pain as they lift their arm up and outwards. The pain often arises when their arm reaches about sixty degrees of elevation. Once they get a bit beyond the ninety degree point, the pain eases again or goes away completely.
If a doctor or therapist resists the patients attempt to lift their arm outwards from the side then the pain will become more pronounced.
Your doctor may perform a maneuver called the Impingement Test to determine whether their is inflammation and impingement in the bursa or the tendons of the shoulder. You can see how this is done here
It is sometimes necessary for the doctor to exclude other problems by performing blood tests or by arranging x-rays or scans. An ultrasound scan is often the most helpful test.
Sometimes MRI scan is required to confirm the diagnosis of shoulder impingement syndrome.
One of the most important aspects of treating shoulder impingement syndrome is to stop doing the movement or activity that provoked it in the first place. Of course this may be easier said than done but you might consider changing your technique or equipment if you are involved in sport. If your impingement has been triggered by work then give some thought to changing the way that you tackle your job tasks and activities.
Treatment options for shoulder impingement include:
painkiller or anti-inflammation medication
physical therapy from a physiotherapist, chiropractor or osteopath
