Knee > Baker's Cyst

What is a Baker's Cyst?

A baker's cyst (popliteal cyst) is a non-cancerous bulge in the back of your knee that protrudes from the soft tissue just above your calf muscle. The bulge occurs when the synovial membrane, which produces fluid that lubricates the area around your knee cartilage, is flooded with fluid. The excess fluid leads to swelling, which can hinder knee movement and cause discomfort.

A baker's cyst is usually an outgrowth of other knee problems. The most common cause of baker's cyst in adults is arthritis. Meniscus tears, cartilage damage, and inflammation of the joint lining can also cause a baker's cyst to form. No particular sports or activities are associated with causing baker's cysts.

Unless it is large, a baker's cyst is not an emergency situation. Treatments are generally not prescribed for the cyst itself. Arthritis or a meniscus tear is often associated with a baker's cyst, so your surgeon may elect to treat your underlying condition with ice, anti-inflammatory medicines, or arthroscopic meniscus surgery. In adults, a baker's cyst sometimes continues to grow until it is treated. Your ability to bend your knee may become limited. Sometimes baker's cysts burst and cause pain in the calf. Rarely, a blood clot in the calf, known as deep venous thrombosis, develops, which may be treated with blood thinners. Large cysts may compress tendons, nerves, and blood vessels in the knee, causing pain and blocking normal circulation, but fortunately this is extremely rare.

There are usually three parts to an orthopedic evaluation: medical history, physical examination, and tests your physician may order.

Your doctor will likely ask you when you noticed your cyst, how it has been feeling since the pain began, and if your knee has been previously injured. Physicians also typically ask about other conditions, such as diabetes and allergies, and medications currently being taken. The doctor may also ask about your physical and athletic goals ­ information that will help him decide what treatment might be best for you in achieving those goals.

A physician usually can make an early assessment of an injury by feeling around the area. Because baker's cysts have a characteristic location and feel in most people, physicians can usually make a quick and accurate diagnosis without the use of instruments or tests. The key to diagnosing a baker's cyst is finding the underlying cause. While asking you questions to pinpoint your pain, physicians also test ligament and tendon strength by checking your knee's range of motion. Depending on what your physician suspects is causing the baker's cyst, you may undergo a more thorough physical exam to diagnose arthritis, meniscus tears, cartilage damage, or other knee problems.

Should your physician require a closer look, MRI (magnetic resonance imaging) is generally the best method for obtaining a clear picture of a baker's cyst. The accumulation of joint fluid is easily visible as a white or brightly colored bulge. MRI can sometimes be used to catch small baker's cysts before they become large and visible to the eye. Ultrasound tests are also frequently used to diagnose a baker's cyst. This is a painless test that is performed by a radiologist or technician who applies a small handheld device to your skin and looks for the cyst on a video monitor. Depending on other knee problems associated with baker's cyst, your physician may order appropriate tests to make a separate diagnosis.

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