Dancing with the Stars contestant, Ralph Macchio, has been out of rehearsals several times this week due to pain caused by a ruptured cyst (called a Baker’s cyst) behind his knee. The 49 year old, former Karate Kid, tweeted:
“Have missed days of rehearsal this week. Had a ruptured cyst on the back of my knee causing acute pain. Hoping to be able to perform tonight!”
So far, it looks like Macchio will be dancing tonight, although he will be “rough around the edges w/o rehearse time.”
A Baker’s cyst is a buildup of joint fluid (synovial fluid) that forms behind the knee. It is noticed as a swelling at the back of the knee. The swelling is due to an increase in synovial fluid – the fluid that lubricates the knee joint. When pressure builds up, fluid bulges into the back of the knee.
Baker’s cyst commonly occurs with:
A large cyst may cause some discomfort or stiffness, but there are often no symptoms. There may be a painless or painful swelling behind the knee. The cyst may feel like a water-filled balloon. Sometimes, the cyst may break open (rupture), causing pain, swelling, and bruising on the back of the knee and calf.
NOTE: It is important to know whether pain or swelling is caused by a Baker’s cyst or a blood clot. A blood clot (deep venous thrombosis) can also cause pain, swelling, and bruising on the back of the knee and calf. A blood clot may be dangerous and requires immediate medical attention.
During a physical exam, the doctor will look for a soft mass in the back of the knee. If the cyst is small, comparing the affected knee to the normal knee can be helpful. There may be limitation in range of motion caused by pain or by the size of the cyst. In some cases there will be signs and symptoms of a meniscal tear.
Transillumination, or shining a light through the cyst, can show that the growth is fluid filled.
Often no treatment is needed. The health care provider can watch the cyst over time. If the cyst is painful, the goal of treatment is to correct the problem, such as arthritis or a meniscus tear. The cyst is usually not removed because it can come back. The surgery may also damage nearby blood vessels and nerves. Sometimes, a cyst can be drained (aspirated) or, in rare cases, removed with surgery if it becomes very large or causes symptoms.
A Baker’s cyst will not cause any long-term harm, but it can be annoying and painful. The symptoms of Baker’s cysts usually come and go. Long-term disability is rare. Most people improve with time or arthroscopic surgery.