Baker’s Cyst (Popliteal Cyst)
(Part 1)
Baker’s cysts, also known as popliteal cysts, are one of the most common disorders in the knee.
These fluid-filled cysts form a lump at the back of the knee that often causes stiffness and discomfort.
The condition is named after the 19th century surgeon who first described it, Dr. William Morrant Baker.
Baker’s cysts typically result from a problem inside the knee joint, such as osteoarthritis or a meniscus tear.
These conditions cause the joint to produce excess fluid, which can then go out a one-way valve in the back of the knee, leading to the formation of a cyst.
Most Baker’s cysts will improve with nonsurgical treatment that includes changes in activity and anti-inflammatory medications.
Some cysts may even go away on their own, with no treatment at all.
Anatomy
The knee joint is filled with a clear, hay-colored fluid (synovial fluid) that acts as a lubricant to help reduce friction within the joint. Small fluid-filled sacs called bursa cushion the joint and help reduce friction between the muscles and other surrounding structures.
Cause
In adults, Baker’s cysts usually result from an injury or condition that causes swelling and inflammation inside the knee joint, such as:
∙ Osteoarthritis
∙ Rheumatoid arthritis
∙ Meniscus tear
∙ Anterior cruciate ligament (ACL) tear
∙ Other conditions that damage the tissues inside the joint
In response to this inflammation, the knee produces excess synovial fluid, which travels behind the knee and exits via a one-way valve, pooling in the popliteal space. The fluid sac then swells and bulges, forming a Baker’s cyst.
In younger patients, Baker’s cysts often have no known cause. (To be continued)