What is impingement syndrome?

Impingement syndrome is a common shoulder condition seen in active adults. This condition is closely related to shoulder bursitis and rotator cuff tendinitis. These conditions may occur alone or in combination.

In most parts of the body, the bones are surrounded by muscles. In the shoulder region, however, the muscle and tendons are surrounded by bone. If one taps on the top of the shoulder, bone can be felt immediately under the skin. Underneath that bone is the rotator cuff, a group of muscles and tendons that we use to lift the arm up overhead. The rotator cuff is sandwiched between the arm bone and the top of the shoulder (acromion). This unique arrangement of muscle and tendon between bone contributes to the development of impingement syndrome (shoulder bursitis, rotator cuff tendinitis).

When an injury to the rotator cuff occurs, it responds by swelling much the way an ankle does when it is sprained. However, because the rotator cuff is surrounded by bone, its swelling causes a number of events to occur. The pressure within the tendon increases, resulting in compression (squeezing) and loss of blood flow in the capillaries (small blood vessels).

When the blood flow is reduced, the tendon tissue begins to fray much like a rope. As the tissue swells, it results in the classic features of a pain like a toothache. Pain is made worse by actions such as reaching up behind the back and reaching up overhead. Pain during the night from this shoulder condition may cause a loss of sleep, and can be a sign of a more serious injury to the rotator cuff, including the development of a small tear or hole in the tendon. This is what is known commonly as a rotator cuff tear.

What are the symptoms of impingement syndrome of the shoulder?

The symptoms of shoulder impingement syndrome include difficulty reaching up behind the back, pain when the arms are extended above the head, and weakness of the shoulder.

In cases of complete tearing of the rotator cuff, patients have very significant weakness and sometimes cannot raise their arm against gravity. In addition, some patients will have a rupture (tear) of their biceps muscle tendon as part of this continuing impingement process.