A bursa is a small, fluid-filled sac that acts as a cushion between a bone and other moving parts, such as muscles, tendons, or skin. Bursitis occurs when a bursa becomes inflamed. People get bursitis by overusing a joint. It can also be caused by an injury. It usually occurs at the knee or elbow. Kneeling or leaning your elbows on a hard surface for a long time can make bursitis start. Doing the same kinds of movements every day or putting stress on joints increases your risk.

Symptoms of bursitis include pain and swelling. Your doctor will diagnose bursitis with a physical exam and tests such as x-rays and MRIs. He or she may also take fluid from the swollen area to be sure the problem isn’t an infection.

Infection of a bursa, referred to as “septic bursitis,” may occur following trauma to the nearby skin. If a bursa becomes infected, the skin in the area around the bursa usually becomes red, warm, and swollen. Excess fluid may also accumulate within an infected bursa. The elbow and the knee are the most common sites of an infected bursa, often as a result of injury to the overlying skin. When redness and swelling are present, urgent medical attention may be necessary to determine if an infection is present.

Treatment of non-septic bursitis typically includes rest, pain medicines, or ice. If there is no improvement, an injection into the area around the swollen bursa may be recommended. If the joint still does not improve after 6 to 12 months, you may need surgery to repair damage and relieve pressure on the bursa.