A Baker’s cyst is a fluid-filled cyst that causes a bulge and a feeling of tightness behind your knee. The cyst can form when joint-lubricating fluid fills a cushioning pouch (bursa) at the back of your knee. The pain can get worse when you fully flex or extend your knee or whenever you’re active.
A Baker’s cyst can sometimes burst (rupture), resulting in fluid leaking down into your calf. This can cause sharp pain, swelling and redness in your calf.
In some cases, a Baker’s cyst causes no pain, and you may not notice it. If you do have signs and symptoms, they might include: Swelling behind your knee, and sometimes in your leg. Comparing both knees will offer you insight as to if one is much larger than the other. It has been described as feeling like a water-filled balloon.
It may cause mild discomfort or pain and tenderness at the posterior aspect of the knee. Baker’s cysts can produce neuropathy by direct pressure on the nerve, either gradually or suddenly. The most dramatic complication is acute rupture with the clinical presentation often called the pseudothrombophlebitis syndrome.