A Baker's Cyst, also called a 'popliteal cyst,' is a collection of fluid in the back of the knee. Calling this problem a cyst is misleading for patients as a Baker's Cyst is not a growth. A Baker's Cyst is the name given to a collection of fluid in the back of the knee. The fluid within a Baker's Cyst is normal joint fluid that has been over-produced, usually because of inflammation from within the knee. A Baker's Cyst is not a tumor or cancer, and cannot spread to other parts of the body.
The most common causes of Baker's Cysts are the common causes of excess fluid in the knee. These causes of fluid accumulation include:anti-inflammatory medications, cortisone injections, or may include surgery such as knee arthroscopy.