Any inflammation of a bursa. Bursae are synovial pouches, positioned to minimize friction between moving parts of the body. They are cystic in appearance and are filled with fluid. More than 80 bursae have been identified on each side of the body around joints and between tendons, muscles, and ligaments. In many cases, they are continuous with or near a regular joint cavity. It is generally thought that bursae exist as normal but irregularly apparent structures, but there is some evidence that they are pathologic alterations of connective tissue produced by irritation and friction. In any case, they rarely produce symptoms unless inflammation occurs. Bursitis most often occurs near the shoulder, hip, elbow, or knee.