Shoulder injury or trauma. Falling or banging the shoulder on a hard surface could cause the bursa to fill with blood and its lining to become inflamed. Even though the body reabsorbs the blood, the bursa lining may stay inflamed, causing bursitis symptoms. This is called traumatic bursitis.
Repetitive pressure on the shoulder. Most often shoulder bursitis is caused by frequent "mini-traumas," which can cause the same problems as a single, more serious trauma. People who must lift their arms overhead for work or sports are more prone to developing shoulder bursitis over time. People at a higher risk of developing shoulder bursitis include painters, wallpaper hangers, tennis players, swimmers and baseball pitchers. Age. While people of any age can be affected, advanced age increases the chances of developing shoulder bursitis.
Poor Posture. People who hunch their shoulders decrease the space between the acromion and the glenohumeral shoulder joints, making it more likely that the soft tissue in between will become squeezed and irritated.
Bacterial infection of a bursa. An infection of the bursa is known as septic bursitis. Certain medical conditions and medications suppress people's immune systems and make them more susceptible to septic bursitis. For example, people with cancer, HIV/AIDS, lupus, alcoholism, chronic obstructive pulmonary disease (COPD), and diabetes may be more likely to develop septic bursitis.
History of inflammation of the bursa. Patients who have had bursitis in the past are more likely to develop it again.
Bone spurs or calcium deposits. The shoulder's bursae and other soft tissue can become irritated by bone spurs, also called osteophytes, that grow on the underside of the acromion. Calcium deposits, which are small collections of calcium that are often small and soft but can grow and harden over time, can also cause irritation.