Syringe filled with fluid drained from the swollen elbow of a 57 year old female patient with olecranon bursitis. Bursitis is inflammation of a bursa, a fluid-filled sac that cushions and lubricates areas where tissues, such as muscles and tendons, move over bone. There are many bursae in the body; the olecranon bursa is over the point of the elbow. Bursitis is caused by repetitive movement, trauma or prolonged and excessive pressure on the bursa, for example resting the elbows on a hard surface. Inflammation makes normal movement painful. Treatment is with rest, anti-inflammatory drugs and in severe cases the bursa may need to be drained.