Bursitis is caused by inflammation of a bursa, a small jelly-like sac that usually contains a small amount of fluid. Bursae are located throughout the body, most importantly around the shoulder, elbow, hip, knee, and heel. They act as cushions between bones and the overlying soft tissues, and help reduce friction between the gliding muscles and the bone. The bony point of the hip is called the greater trochanter. It is an attachment point for muscles that move the hip joint. The trochanter has a fairly large bursa overlying it that occasionally becomes irritated, resulting in hip bursitis (trochanteric bursitis).