Baker’s cysts, also calledpopliteal cysts, are fluid-filled sacs brought on by excess knee-joint fluid.
This common condition can occur with arthritis or injuries that lead to swelling.
This article explains the causes and symptoms of a Baker’s cyst and how it is diagnosed and treated.

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Simply put, a Baker’s cyst can develop after the joint capsule becomes damaged or weakened.
Symptoms
A Baker’s cyst can be soft to the touch and slightly tender.
When you extend your knee, this can make a Baker’s cyst tighter or more painful.
A Baker’s cyst can actually swell or shrink.
The fluid from the ruptured cyst is absorbed by the body.
When this happens, the Baker’s cyst temporarily disappears, but it usually comes back.
If you have pain and swelling behind your knee, seek medical attention.
Surgical removal of a Baker’s cyst is an option if you find the cyst painful or particularly bothersome.
Even after it is surgically removed, a Baker’s cyst may recur.
In some cases, surgery may be recommended.
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