Baker’s cysts, or more correctly popliteal cysts, are fluid filled structures, located in the back part of the knee. While relatively common and frequently detected on routine knee examination or by feeling a lump behind the knee, they are not associated with being a baker! In fact, most of the general public and even some clinicians commonly misunderstand the cause and treatment of these cystic structures.
Bakers cysts, named after the physician who originally described them in the 1800’s, essentially are bursal sacs that become distended with fluid exiting from the back part of the knee joint. This pressurized fluid enters into the bursa via a one-way valve mechanism causing swelling and possibly a painful lump behind the knee. They are detected on imaging studies like ultrasound and MRI’s but cannot be visualized on a standard x-ray. While these cysts can cause local symptoms from the pressure they create and may even rupture if extremely large, their presence is often indicative of an underlying problem within the knee joint itself. Conditions, which frequently cause Baker’s cyst, include knee effusions (water on the knee), cartilage injury, meniscal tears, and osteoarthritis.
While it seems tempting to simply have the cyst drained in the hopes of resolving the swelling, the success rate of this treatment can be poor as the bursa will often refill with fluid. More importantly, the underlying problem itself within the knee joint needs to be addressed in order for the cyst to be appropriately reduced in size. While surgery may be indicated in rare circumstances, most non-surgical treatments can be extremely helpful in resolving symptoms from a Baker’s cyst.
So remember the next time someone tells you they have a Baker’s cyst, tell them it’s not from baking and more significantly, their knee should be examined to determine precisely why they have this common but often misunderstood problem.
Paul Lento, MD is a triple Board Certified Physical Medicine and Rehabilitation physician at 360 ORTHOPEDICS. He specializes in the non-surgical treatment of various musculoskeletal problems that cause pain or loss of function.
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