Bursae are fluid-filled cavities near joints where tendons or
muscles pass over bony projections. They assist movement and reduce friction between
moving parts.
Bursitis can be caused by chronic overuse, trauma, rheumatoid arthritis, gout, or
infection. Sometimes the cause cannot be determined. Bursitis commonly occurs in the
shoulder, knee (washmaid's knee), elbow, and hip. Other areas that may be affected include
the Achilles tendon and the foot.
