What is shoulder impingement syndrome?

Impingement syndrome is a common shoulder condition seen in active adults, especially as they get older. 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 you tap the top of your shoulder, you can feel bone 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 bones contributes to the development of impingement syndrome (shoulder bursitis, rotator cuff tendinitis).

When the rotator cuff is injured, it swells in much the same 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, which results in compression (squeezing) and reduced 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, you might feel pain similiar to a toothache. The pain is made worse by reaching (up behind the back, overhead, etc.). Pain from this shoulder condition during the night may cause a loss of sleep. This can also be a sign of a more serious injury to the rotator cuff, including the development of a small tear or hole in the tendon (which is referred to as a rotator cuff tear).

What are the symptoms of shoulder impingement syndrome?

The symptoms of shoulder impingement syndrome include:

  • Difficulty reaching up behind the back
  • Pain when the arms are extended above the head
  • Shoulder weakness

In cases in which the rotator cuff has torn completely, 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.

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