Bursa are fluid-filled sacs that act as a cushion between bones, tendons, joints, and muscles.  Trochanteric Bursitis is inflammation of the bursa at the outside point of the hip, the Greater Trochanter, and this irritated and inflamed bursa commonly causes hip pain.   Causes of Trochanteric Bursitis Injury from a fall or hard hit to the outside of the hip can cause the bursa to fill with blood and inflamed Lying on one side for a prolonged period. ...