Bursa is a sac that is filled with fluid, when this bursa becomes inflamed due to any reason it is called bursitis. There are many bursae in our body and works as a cushion between the bone and soft tissues, one bursa is present over the trochanter (outer edge of the hip) when this trochanter bursa becomes inflamed it is called trochanteric bursitis. Bursitis is a common cause of hip pain.