Baker's cyst
A Baker's cyst is a fluid-filled cyst that causes a bulge and a feeling of tightness behind your knee. The pain can get worse when you fully flex or extend your knee or when you're active. A Baker's cyst, also called a popliteal (pop-luh-TEE-ul) cyst, is usually the result of a problem with your knee joint, such as arthritis or a cartilage tear. Both conditions can cause your knee to produce too much fluid, which can lead to a Baker's cyst. Although a Baker's cyst may cause swelling and make you uncomfortable, treating the probable underlying problem usually provides relief. Symptoms In some cases, a Baker's cyst causes no pain, and you may not notice it. If you do have signs and symptoms, they might include: -Swelling behind your knee, and sometimes in your leg -Knee pain -Stiffness and inability to fully flex the knee Cause A lubricating fluid called synovial (sih-NO-vee-ul) fluid helps your leg swing smoothly and reduces friction between the moving parts of your knee. But sometimes the knee produces too much synovial fluid, resulting in buildup of fluid in an area on the back of your knee (popliteal bursa), causing a Baker's cyst. This can happen because of: -Inflammation of the knee joint, such as occurs with various types of arthritis -A knee injury, such as a cartilage tear
