Baker’s cysts, also called popliteal cysts, form when fluid collects behind the knee. Many people have no symptoms, while others may experience pain or stiffness when fully flexing or extending the knee. If the cyst bursts, the calf may swell, and more intense pain can develop. Generally, treating the cause of Baker’s cysts provides relief and alleviates the symptoms. There are many possible causes, but the vast majority are varieties of arthritis. Anything that can cause inflammation of the knee can cause a Baker's cyst.
Synovial fluid surrounds the knee joint. This fluid is contained inside a membrane and plays an integral role in smooth movement of the knee. The synovial fluid can occasionally flow from the knee joint to the back of the knee, which causes swelling and a Baker’s cyst. This is usually the result of the body producing too much synovial fluid because of inflammation or knee injuries.
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