Bursitis is a painful condition that affects the joints. Bursae are fluid-filled sacs that act as a cushion between bones, tendons, joints, and muscles. When these sacs become inflamed it is called bursitis.

It is a relatively common condition, but many people treat it at home and do not see a doctor, so it is hard to know how common it is. There are over 150 bursae in the human body. They cushion and lubricate points between the bones, tendons, and muscles near the joints. The bursae are lined with synovial cells. Synovial cells produce a lubricant that reduces friction between tissues. This cushioning and lubrication allow our joints to move easily. When a person has bursitis, or inflammation of the bursa, movement or pressure is painful. Overuse, injury, and sometimes an infection from gout or rheumatoid arthritis may cause bursitis. Tennis elbow is one type of bursitis.