Impingement syndrome

Impingement syndrome is a common condition affecting the shoulder often seen in aging adults. This condition is closely related to shoulder bursitis and rotator cuff tendonitis. These conditions may occur alone or in combination.

In virtually all parts of your body, bones are the innermost structures and are surrounded by muscles. When an injury occurs to the rotator cuff muscles, they respond by swelling. However, because the rotator cuff muscles are surrounded by bone, when they swell, a series of other events occur.

The pressure within the muscles increases, which results in compression and loss of blood flow in the small blood vessels. When the blood flow decreases, the muscle tissue begins to fray like a rope. Motions such as reaching up behind the back and reaching up overhead to put on a coat or blouse, for example, may cause pain.

© 2005-2013 WebMD, LLC. All rights reserved.
Source article on WebMD

Source: MedicineNet.com
http://www.medicinenet.com/impingement_syndrome/article.htm