Bursitis is inflammation of a bursa. A bursa is a small jelly-like sac that acts as a cushion between the bone and the overlying soft tissues to reduce friction between them. The bony point of the hip (Greater Trochanter) has a fairly large bursa that can become irritated.
There are two major bursae of the hip, the Trochanteric bursa and the Ischial bursa. The Trochanteric bursa is located on the outside of the hip.