A bursa (plural bursae or bursas; Latin: Bursa synovialis) is a small flui-filled sac made of white fibrous tissue and lined with synovial membrane. It provides a cushion between bones and tendons and/or muscles around a joint; bursae are filled with synovial fluid and are found around almost every major joint of the body; when they become inflamed, the condition is called bursitis.