What is a Popliteal Cyst?
A popliteal cyst is a benign fluid-filled swelling that appears at the back of the knee in some children. It connects with a cyst that we all have at the back of our knees. This cyst oils the hamstring tendons as they move over the back of the knee so they don’t fray through. The cyst has a fancy name - the semi-membranous bursa-but most people find “popliteal cyst” easier to say.
Why does it appear?
Children have a connection between the back of the knee and the main knee joint. This allows fluid from the knee to fill the cyst at the back. As children get older, this connection closes and the cyst goes away.
What should be done about it?
Nothing. These cysts will always go away eventually without treatment although they can come and go for 1-2 years before that happens.
We don’t recommend operations to remove these cysts as this is more painful than having the cyst and they often come back after an operation.
There are no other treatments which have been shown to make any difference.
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