Shoulder pain is the third most common complaint in orthopedic practice, and shoulder impingement is often the cause. 1 Garving C, Jakob S, Bauer I, Nadjar R, Brunner UH. Impingement Syndrome of the Shoulder. Dtsch Arztebl Int. 2017;114(45):765-776. Shoulder impingement can make reaching overhead difficult, cause pain or discomfort when sleeping, and affect range of motion.

What Is Shoulder Impingement?

Motion of abduction with shoulder impingement

Shoulder impingement occurs when the arm is raised (abduction). During this motion, the supraspinatus muscle, the bicep muscle tendon, and/or the bursa can become pinched between the bones of the shoulder.

Shoulder impingement—sometimes called subacromial impingement—refers to the painful pinching of the muscles, tendons, or other soft tissues between the bones and/or ligaments of the shoulder.


In the shoulder, soft tissues are sandwiched between bones
The shoulder includes an area where soft tissues, such as the bicep tendon, rotator cuff, ligaments, and bursa, are sandwiched between bones. This area, called the subacromial space, is located above the shoulder’s ball-and-socket joint and below the acromion, the top-most bone of the shoulder.

When a person raises his or her arm, the subacromial space becomes smaller. In a case of shoulder impingement, raising the arm causes the pinching of soft tissues, which results in shoulder pain and other symptoms.

What Causes Shoulder Impingement?

Shoulder anatomy including the AC joint, glenohumeral joint, and subacromial space

The shoulder joint is a ball-and-socket joint supported by soft tissues. Its design allows for a high degree of flexibility but also makes the shoulder susceptible to injuries such as shoulder impingement.


A person may have one or more issues that leads to shoulder impingement, including:

  • Overuse, such as from swimming, baseball, or occupations that require frequent, heavy overhead lifting. Overuse of a joint can irritate and inflame soft tissues, causing them to swell. These swollen tissues are more likely to become pinched in the subacromial space.
  • A narrow subacromial space, caused by either natural (inherited) bone shape or arthritic changes to the bones.
  • Injuries, such as a rotator cuff tear or torn labrum. In some cases, untreated shoulder impingement can actually cause these injuries.

People who have shoulder impingement can benefit from knowing its symptoms, the causes and risk factors, and how it is diagnosed and treated.