Bursitis (bur-SY-tis) is a painful condition that affects the small, fluid-filled sacs — called bursae (bur-SEE) — that cushion the bones, tendons and muscles near your joints. Bursitis occurs when bursae become inflamed. The most common locations for bursitis are in the shoulder, elbow and hip. But you can also have bursitis by your knee, heel and the base of your big toe. Bursitis often occurs near joints that perform frequent repetitive motion. Treatment typically involves resting the affected joint, but may also include and protecting it from further trauma, additional treatments may include physical therapy or medication, as well as injections for immediate relief.