Baker's Cyst

Medically Reviewed By William C. Lloyd III, MD, FACS
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What is a Baker’s cyst?

A Baker’s cyst is a soft, fluid-filled cyst that develops behind the knee. The knee joint is the largest joint in your body. The bones that form it include the thighbone, shinbone and kneecap. Inside the joint, synovial fluid cushions and lubricates the joint components to help them slide past each other. Damage or disease inside the knee stimulates your body to make more synovial fluid. A Baker’s cyst can form when this excess synovial fluid leaks out into the popliteal bursa at the back of the knee. Other names for the cyst include Baker cyst, popliteal cyst, and synovial cyst.

People with knee problems are at increased risk of developing a Baker’s cyst. This includes having knee conditions, such as arthritis and gout, or knee injuries or damage, such as a meniscal tear.

Baker’s cysts are often painless and some people never notice them. If Baker’s cyst symptoms develop, they can include pain, stiffness or tightness, and a bulge behind the knee. Symptoms may be worse after being active or standing for a long time. Symptoms of a ruptured Baker’s cyst include pain, swelling of the calf, and bruising behind the knee.

It’s possible for Baker’s cysts to go away on their own. The body simply resorbs the excess fluid. They can also burst and release fluid under the skin that will eventually be resorbed. If a Baker’s cyst persists and causes symptoms, treating the underlying condition is the best way to resolve it. Doctors may also recommend physical therapy, anti-inflammatory medicines, or fluid drainage.

The symptoms of a Baker’s cyst can mimic those of a DVT (deep venous thrombosis) blood clot. It’s important to see your doctor promptly if you have symptoms to make sure it is a harmless cyst and not a blood clot. A DVT can lead to life-threatening complications and requires immediate medical attention.

What are the symptoms of a Baker’s cyst?

Often, people with Baker’s cysts don’t have symptoms other than a bulge at the back of the knee. In fact, many people may not even know they have a cyst, especially if it is small. Doctors may find them during imaging exams for other reasons.

Common symptoms of a Baker’s cyst
Common symptoms of a Baker’s cyst include:

  • Bulge or sense of fullness at the back of the knee that may go away when you bend your knee
  • Stiffness or tightness that may limit the ability to fully flex or extend the knee

These symptoms often get worse with activity or prolonged periods of standing or keeping the knee fully extended. Symptoms can also come and go. If the cyst ruptures, you may notice calf swelling, pain, and bruising behind the knee.

Serious symptoms that might indicate a life-threatening condition

Baker’s cyst symptoms are very similar to a more dangerous condition—a DVT blood clot. A DVT can lead to a life-threatening complication called a PE (pulmonary embolism). See your doctor right away to make sure you do not have a DVT. Seek immediate medical care (call 911) if you, or someone you are with, have any symptoms of a life-threatening PE including:

What causes a Baker’s cyst?

A Baker’s cyst occurs when excess synovial fluid leaks into the popliteal bursa. Normally, synovial fluid circulates through your knee joint and in and out of bursae, which are cushioning sacs. When there is too much synovial fluid, pressure drives the fluid into the popliteal bursa causing a Baker’s cyst. The pressure increases even more when the knee moves with activity or there is prolonged force on it from standing. The body produces excess synovial fluid in response to damage or disease within the joint.

What are the risk factors for a Baker’s cyst?

Having a knee condition that results in disease or damage to the joint puts people at risk of developing a Baker’s cyst. These conditions include:

  • Cartilage tears or injuries, especially meniscal tears
  • Gout
  • Ligament tears

Reducing your risk of a Baker’s cyst

It isn’t always possible to prevent a Baker’s cyst, as many people don’t even know they have one. Treating known knee conditions and damage is the best way to reduce the risk.

How is a Baker’s treated?

Baker’s cysts don’t always require treatment. Sometimes, they will go away on their own and often they don’t cause problems that require treatment. If pain and other symptoms are bothersome, your doctor may recommend treatment. The most effective Baker’s cyst treatment is eliminating or controlling the underlying condition. To manage symptoms, doctors often use the following strategies:

  • Anti-inflammatory medicines, including corticosteroid injections into the knee
  • Drainage or aspiration of the cyst to remove the fluid
  • Physical therapy to strengthen the muscles supporting the knee and improve range of motion
  • Rest, ice and elevation

Unless you treat the underlying condition, a Baker’s cyst is likely to recur. Rarely, doctors use surgery to remove very large cysts.

What are the potential complications of a Baker’s cyst?

A Baker’s cyst rarely causes long-term problems or disability. The main complication is a ruptured cyst. While a ruptured Baker’s cyst is not dangerous, the symptoms can be alarming. They can also mimic a DVT blood clot. So, while a Baker’s itself is usually harmless, it’s important to see your doctor to be sure it’s nothing more.

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Medical Reviewer: William C. Lloyd III, MD, FACS
Last Review Date: 2020 May 14
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THIS TOOL DOES NOT PROVIDE MEDICAL ADVICE. It is intended for informational purposes only. It is not a substitute for professional medical advice, diagnosis or treatment. Never ignore professional medical advice in seeking treatment because of something you have read on the site. If you think you may have a medical emergency, immediately call your doctor or dial 911.
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