A Baker’s cyst is a localized accumulation of synovial fluid (joint
fluid) behind the knee. It results from abnormal swelling of a bursa in that location. A bursa is a fluid-filled sac that normally decreases friction (resulting from the movement of joints) between tendons, muscles, and bones.
This condition, named after William Morrant Baker, a British surgeon who first described it, is usually not serious. It does not cause any long-term damage and usually improves on its own with time. In some cases, however, surgery may be necessary.
The exact cause of some Baker’s cysts is unknown. Half of incidences occur in children, appearing as painless masses behind the knee that are more obvious when the knee is straightened. This type may be formed by the connection of a normal bursa with the knee joint.
Other Baker’s cysts come from many conditions that cause swelling and/or damage to the knee joint, including:
A Baker’s cyst may exhibit no symptoms at all. The following are common symptoms of a Baker’s cysts. If you experience any of these symptoms, do not assume it is due to a Baker’s cyst but see your doctor:
Rounded swelling behind the knee about the size of a golf ball
Pain or pressure in the back of the knee joint, which can travel to the calf muscle
Aching or tenderness after exercise and bending the knee
Your doctor will ask about your symptoms and medical history. During a physical exam, the doctor will look for a soft mass in the back of the knee, and compare range of motion (and limitations) of the affected knee to the normal knee. The following tests or procedures may be
Trans-illumination—shining a light through the cyst to show the mass is fluid-filled.
Please be aware that this information is provided to supplement the care
provided by your physician. It is neither intended nor implied to be a
substitute for professional medical advice. CALL YOUR HEALTHCARE PROVIDER
IMMEDIATELY IF YOU THINK YOU MAY HAVE A MEDICAL EMERGENCY. Always seek the
advice of your physician or other qualified health provider prior to
starting any new treatment or with any questions you may have regarding a