Every person has hundreds of bursa scattered throughout the body. The function of a bursa is to decrease friction between two surfaces that move in different directions. They are commonly found where muscles and tendons glide over bones. Bursitis is the inflammation of the bursa, often secondary to overuse, trauma, gout or infection. In the normal state, the bursa provides a slippery surface that has almost no friction. When a bursa becomes inflamed it loses its gliding capabilities, and becomes more and more irritated when it is moved. Bursitis can occur anywhere throughout the body, often occurs in the shoulder and hip.