Is the lump behind my knee a cyst?

Originally Published: September 26, 2003 - Last Updated / Reviewed On: December 29, 2009
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Dear Alice,

I have a 1/2-inch lump inside the back of my leg 2 inches above my knee (there is no visible mark on the skin). It is not painful or bothersome in any way. An acupuncturist thinks it is a cyst. If it is, what kind might it be, what kind of treatment might I get, and how necessary is it?

Dear Reader,

Tuning into the lumps and bumps on your body can help you maintain your health. Your primary health care provider could be your next step to determine if the lump is a cyst and how it can be treated.

Cysts are sacs that are filled with fluid, solid substances, or even air. They can occur in any tissue of the body, but the most obvious cysts are those that occur in the skin. Cysts are most commonly the result of an infection that clogs the sebaceous glands (which produce your skin's oils), or the body's response to a foreign object. Cysts can cause general soreness or tenderness in the surrounding area. Most internal and external cysts, while possibly unsightly and uncomfortable, are not serious health concerns.

A cyst in the back of the knee, similar to the lump you describe in your question, is called a Baker's cyst, named after the physician who first discovered them. This type of cyst occurs when the fluid that helps lubricate the knee joint bulges out from between the bones. While it is sometimes related to arthritis or other conditions causing inflammation to the knees, the cyst itself is usually painless and harmless. There are other possible causes of a lump behind the knee, though, so it's important to have your health care provider check it out to be sure.

If you notice a growth similar to a cyst, your health care provider will generally ask you about any growths and changes that you might have noticed, and will examine the cyst for tenderness and size. If you are a Columbia student, you can schedule an appointment by calling x4-2284 or logging into Open Communicator. If they become infected, cysts can be drained and/or removed. The most common treatment of skin cysts is none at all, since the most cysts pose no health risk.

You are the first line of defense in noticing new and different things about your body. Keep up the good detective work.

Alice