Bursitis is the inflammation of one or more bursae (fluid filled sacs) of synovial fluid in the body. They are lined with a synovial membrane that secretes a lubricating synovial fluid. There are more than 150 bursae in the human body. The bursae rest at the points where internal functionaries, such as muscles and tendons, slide across bone. Healthy bursae create a smooth, almost frictionless functional gliding surface making normal movement painless. When bursitis occurs, however, movement relying on the inflamed bursa becomes difficult and painful. Moreover, movement of tendons and muscles over the inflamed bursa aggravates its inflammation, perpetuating the problem. Muscle can also be stiffened. Signs and symptoms
Bursitis commonly affects superficial bursae. These include the subacromial, prepatellar, retrocalcaneal, and pes anserinus bursae of the shoulder, knee, heel and shin, etc. (see below). Symptoms vary from localized warmth and erythema to joint pain and stiffness, to stinging pain that surrounds the joint around the inflamed bursa. In this condition, the pain usually is worse during and after activity, and then the bursa and the surrounding joint becomes stiff the next morning.Bursitis could possibly also cause a snapping, grinding or popping sound – known as snapping scapula syndrome – when it occurs in the shoulder joint. This is not necessarily painful. Cause
There can be several concurrent causes. Trauma, auto-immune disorders, infection and iatrogenic (medicine-related) factors can all cause bursitis. Bursitis is commonly caused by repetitive movement and excessive pressure. Shoulders, elbows and knees are the most commonly affected.
Steroid therapy may also be considered. In cases when all conservative treatment fails, surgical therapy may be necessary. In a bursectomy the bursa is cut out either endoscopically or with open surgery. The bursa grows back in place after a couple of weeks but without any inflammatory component. See also
Calcific bursitis
Snapping scapula syndrome

References
External links

Bursitis treatment from NHS Direct
Questions and Answers about Bursitis and Tendinitis – US National Institute of Arthritis and Musculoskeletal and Skin Diseases