Bursitis in the shoulder is an inflammatory condition of a bursa, or cushioning sac of tissue, that aids movement in the rotator cuff. The muscles, joints and tendons here provide free movement for the shoulder and upper arm. The most common site for shoulder bursitis is beneath the acromion bone, hugging the glenohumeral joint. The problem can arise with one stressful motion or through overuse of the rotator cuff over time. Bursitis can cause extreme shoulder pain and can severely compromise the patient's range of motion.
Overuse Injuries
Shoulder bursitis is most often caused by overuse of the acromioclavicular or glenohumeral joints and adjacent muscles. According to the University of Chicago Medical Center (UCMC), this can occur during heavy overhead lifting, forceful athletic motions or even passive poor posture. The shoulder pain of bursitis may be exacerbated by related tendinitis or a torn labrum, which is a tear to the protective cartilage between the joint and bursa.
The National Institute of Arthritis and Muskuloskeletal and Skin Diseases (NIAMS) report that shoulder overuse occurs in certain trades, such as carpentry, or in certain disciplines practiced by musicians and athletes. Swimmers, baseball pitchers and tennis players will be aware of the muscle-use patterns that lead to shoulder bursitis. People who practice habitually bad upper-body posture or poor lifting ergonomics, however, may need medical advice to avoid repeating the behavior that damaged the bursa.
Traumatic Injuries
NIAMS reports that direct trauma to the bursa can prompt the inflammatory response of shoulder bursitis. The bursa can sustain a blow from a fall, contact with an object, or residual trauma from dislocation or another violent injury. Any twist, stretch or tear to adjacent soft tissue may inflame the bursa.
When the subacromial bursa swells, it reduces the space normally reserved for shoulder muscle movement, causing pain and effectively restricting the patient's range of motion. If multiple parts of the rotator cuff are involved, a cycle of inflammation and shoulder pain can make it difficult to isolate and diagnose bursitis.
Arthritis and Infection
Other conditions that cause a local inflammatory response can squeeze the bursa and trigger bursitis. As the UCMC notes, arthritis can be a primary source of shoulder pain. Therefore, osteoarthritis, rheumatoid arthritis or monoarthritis associated with gout may require diagnosis in order to treat bursitis.
Although infection is less likely in the subacromial bursa of the rotator cuff than in bursae located in the elbow or knee, septic bursitis is a possibility. Again, the infectious cause must be discovered and addressed in order to fully resolve the bursitis condition.
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