Bursitis is a term applied to inflammation of a bursal sac. A bursal sac is like a deflated balloon, with the inside lined by a very thin layer of lubricating fluid. This sac is found interposed between moving parts of the body where it facilitates movement. It may be found interposed between tendons and bone, between tendon and skin, between tendons and tendons or between skin and bone. This potential cavity can become inflamed from acute or chronic injury. The cavity then fills up with fluid and becomes swollen and painful. Common sites for bursitis are the hip (trochanteric bursitis), shoulder (subacromial bursitis), knee (prepatella bursitis), and elbow (olecranon bursitis).

Bursitis responds very well to acupuncture therapy which decreases inflammation and promotes healing. Recovery is helped by a graded self-exercise program and by modulation of daily activities.