What is a Bursa?

A bursa is a closed, fluid-filled sac whose functions is to cushion and provide a gliding surface to reduce friction between tissues of the body. The major bursae are located adjacent to tendons near large joints, such as in the shoulders, elbows, hips, and knees. When the bursa becomes inflamed, the condition is known as bursitis.

Bursae are lined with special cell tissue known as synovial cells, and are responsible for secreting fluids rich in proteins and collagen. This fluid acts like a lubricant between surfaces high in friction, such as an elbow or shoulder joint, thus allowing tendons and muscles to slide over bone effortlessly. Once this fluid becomes infected, a condition occurs known as bursitis. There are about 160 bursae in the human body and some people have more than others.