Bursitis is a medical condition which involves an inflammation of the bursa, a small fluid filled sac. This sac is located wherever there are bones and tendons, to facilitate a smooth movement of the joint. It acts as a padding or buffer between a bone and a tendon. Inflammation of bursa or bursitis can happen in shoulder, elbow, knee, hip and a few other joints. Shoulder bursitis is the most common amongst these.