This fluid-filled cyst occurs behind the knee and can be caused by arthritis or a cartilage tear. Treating the cause usually provides relief.
A Baker cyst is a fluid-filled growth behind the knee. It causes a bulge and a feeling of tightness. Also called a popliteal (pop-luh-TEE-ul) cyst, a Baker cyst sometime causes pain. The pain can get worse when with activity or when fully straightening or bending the knee.
A Baker cyst is usually the result of a problem with the knee joint, such as arthritis or a cartilage tear. Both conditions can cause the knee to produce too much fluid.
Although a Baker cyst may cause swelling and discomfort, treating the underlying problem that is causing it usually provides relief.
Swelling on the back of one knee may be a Baker cyst. This can form when joint-lubricating fluid fills a cushioning pouch (bursa) at the back of the knee.
In some cases, a Baker cyst causes no pain, and you may not notice it. If you do have symptoms, they might include:
The symptoms may be worse after you've been active or if you've been standing for a long time.
Seek medical attention if you have pain and swelling behind your knee. Though unlikely, these symptoms may be a sign of a blood clot in a leg vein.
A lubricating fluid called synovial (sih-NO-vee-ul) fluid helps the leg swing smoothly and reduces friction between the moving parts of the knee.
But sometimes underlying conditions can cause the knee to produce too much synovial fluid. When this happens, fluid can build up in the back of the knee, leading to a Baker cyst.
This can be caused by:
Rarely, a Baker cyst bursts and synovial fluid leaks into the calf region, causing:
A Baker cyst can often be diagnosed during a physical exam. However, some of the symptoms of a Baker cyst are similar to the symptoms of more-serious conditions, such as a blood clot, aneurysm or tumor. To get more information, your health care provider may order imaging tests, including:
Sometimes a Baker cyst will disappear on its own. Mild symptoms can often be controlled by avoiding activities that trigger them.
However, if the cyst is large and causes pain, you may need treatment.
A nonprescription pain reliever, such as acetaminophen (Tylenol, others) or ibuprofen (Advil, Motrin IB, others) can reduce pain and inflammation.
An injection of steroid medication, such as cortisone, into the knee can reduce inflammation. This may reduce the size of the cyst and relieve pain, but it doesn't always stop the cyst from coming back.
Gentle exercises that improve range of motion and strengthen the muscles around the knee may help it feel better and preserve knee function.
To reduce the size of the cyst, your care provider may drain the fluid from the cyst using a needle. This is called needle aspiration and is often performed with ultrasound guidance.
If a joint problem is causing the cyst, arthroscopic surgery may be performed to repair the problem. For example, if a cartilage tear is causing synovial fluid to collect in the knee, the surgeon removes or repairs the torn cartilage. At the same time, the surgeon can also remove fluid from the cyst.
Rarely, surgery is needed to remove the cyst. This approach is typically used only after other treatment options haven't helped the pain and the ability to walk or perform other activities is still limited.
If arthritis is causing the cyst, your health care provider may advise you to take some or all of the following steps:
Here's some information to help you prepare for your appointment.
Your time with your care provider may be limited, so preparing a list of questions can help you make the most of your time together. For a Baker cyst, some basic questions to ask include:
Don't hesitate to ask other questions.
Your health care provider is likely to ask you a number of questions, such as: