A Baker’s cyst is a common finding in adults with knee pain. More specifically called popliteal synovial cysts, they are protrusions in the back of the knee. In this article, I answer some common questions that patients often have with these cysts.

Where are they located?

They’re usually found in the back of the knee between the semimembranosus and the medial head of the gastrocnemius.

What symptoms could a patient have with a Baker’s cyst?

A patient often complains of achy discomfort in the back of the knee. He might notice swelling in the back of the knee. If the cyst is large, he might feel it in the back of the knee.

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Ask Dr. Geier – Is surgery necessary for a meniscus tear?
Ask Dr. Geier – Arthritis after a meniscus tear

Cartilage damage in the knee
Note the frayed articular cartilage on the end of the femur (red arrow). This is the appearance of cartilage in more advanced arthritis.

How does a Baker’s cyst develop?

A one-way valve can develop in the posterior capsule, or the joint lining at the back of the knee. Joint fluid can flow out of the knee joint and into the cyst, but it cannot flow back into the knee.

What other knee conditions are associated with Baker’s cysts?

The vast majority of Baker’s cysts are associated with other pathology within the knee, including meniscus tears, osteoarthritis and other injuries.

What studies can reveal a Baker’s cyst?

X-rays won’t show a cyst but they can be important to show bony changes like osteoarthritis. Ultrasound can demonstrate the cyst. The study is relatively inexpensive, and it doesn’t involve radiation. Ultrasound doesn’t demonstrate the pathology within the knee, though. MRI is usually considered the best test because it can show the cyst and any other conditions, like meniscus tears.

Also read:
Ask Dr. Geier – Meniscus Tears
Meniscus Tears – Recovery

How is a Baker’s cyst treated?

Usually orthopedic surgeons don’t pursue treatment for the cyst itself. A trial of nonoperative treatment can often help. If symptoms persist, the surgeon usually treats the problem within the knee, such as arthroscopic surgery to trim out a meniscus tear. Rarely surgery to open the back of the knee and treat these cysts can be necessary.

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Frush TJ, Noyes FR. Baker’s Cyst: Diagnostic and Surgical Considerations. Sports Health. 2014;7(4):359-65.