Even Mr. Miyagi couldn’t keep Ralph Macchio from being eliminated from the TV show “Dancing With the Stars” after the former “Karate Kid” star suffered a ruptured Baker’s cyst behind his knee.

A Baker’s cyst is a buildup of joint fluid, known as synovial fluid, that forms behind the knee. When pressure builds up, fluid bulges into the back of the knee, sometimes causing pain or stiffness. But often there are no symptoms. The cyst may feel like a water-filled balloon. And sometimes the cyst may break open, causing pain, swelling and bruising on the back of the knee and calf.

If you incur pain or swelling behind the knee, it’s important to have a doctor check it out, to rule out a blood clot or a tumor. The cyst may also be caused by other damage, such as a meniscal tear, that needs to be repaired.

Often no treatment is needed. Your doctor may want to watch the cyst over time. In some cases, the cyst may need to be drained or surgically removed. But generally, cysts are left in place because they may return anyway, and surgery can damage nearby blood vessels and nerves.

— Markian Hawryluk, The Bulletin

Source: National Library of Medicine