Baker’s Cyst

A Baker’s cyst, also known as popliteal cyst or popliteal synovial cyst, is a fluid-filled swelling that forms behind the knee. It’s named after the doctor who first described it, William Morrant Baker.

A Baker’s cyst is filled with synovial fluid (lubricating fluid usually found inside the knee joint). This fluid helps the leg swing smoothly and reduces rubbing (friction) between the moving parts of the knee.

Sometimes, an underlying condition can cause the knee to produce too much fluid. This fluid can build up and leak into the extra space (or form a pocket-like pouch) behind the knee. The cyst can vary in size from very small to large. Rarely does it develop on both knees at the same time.

What causes Baker's cysts?

A Baker’s cyst is usually caused by an underlying problem in the knee joint, such as:

• Arthritis (osteoarthritis or rheumatoid arthritis)
• Knee injury (overuse injuries, meniscus tear, sprains and fractures)
• Inflammation of the knee joint (gout)

Anyone can develop a Baker’s cyst. However, some people might be more likely to develop this type of cyst:

• Older adults 
• People with previous injuries or trauma to the knee
• Chronic (ongoing) conditions like osteoarthritis or rheumatoid arthritis
• People who play high-impact sports or activities

A Baker’s cyst might not cause any symptoms. It will more often be seen on an imaging test, like an MRI, done for other reasons. If you do have symptoms, they might include:

• Swelling and inflammation behind the knee
• Knee pain
• Stiffness and limited movement
• A feeling of tightness or fullness behind the knee

These symptoms usually worsen when standing for a long time or being active. If your knee pain or swelling is affecting your daily activities, it’s important to seek medical attention to prevent further complications.

Can a Baker’s cyst cause complications?

In rare cases, a Baker’s cyst might cause complications. These include:

• Bursting: Sometimes, the cyst can burst (rupture), leading to the fluid leaking into the calf muscle. This can cause sharp pain, swelling and redness in the calf, which might be mistaken for a blood clot.
• Limited mobility: Because the cyst can restrict the movement of the knee, it might be hard to do everyday activities, like walking, climbing stairs or kneeling.
• Pressure on the blood vessels: A large cyst might press on blood vessels in the leg, leading to poor blood flow. This can cause symptoms like swelling, pain or even numbness in the lower leg.
• Chronic pain: If the underlying cause of the cyst isn’t treated, the cyst might return and cause ongoing pain and discomfort. Left untreated, a Baker’s cyst can worsen, potentially leading to surgery.

If you have symptoms of a Baker’s cyst, see your health care provider. They will diagnose a Baker’s cyst with a physical exam, looking for a lump on the back of your knee. Since the symptoms of a Baker’s cyst are like those of other conditions, your provider might order imaging tests, such as an ultrasound, X-ray or MRI. Early diagnosis is key to avoiding long-term complications and pain. Understanding the cause of a Baker's cyst can help guide the right treatment for you.

Treating a Baker’s cyst depends on the underlying cause and severity of your symptoms. Usually, you won’t need treatment if you don’t have symptoms. Sometimes a cyst will go away on its own. The fluid in the cyst is absorbed back into your body.

However, if the cyst is large and causes pain, you might need treatment. Options might include:

• Rest, Ice, Compression and Elevation (RICE method): Rest the knee and apply ice to reduce swelling and pain. Compress your knee with a wrap, sleeve or brace and elevate your leg when possible.
• Medications: Over-the-counter (OTC) pain relievers like ibuprofen (Advil®) or acetaminophen (Tylenol®) can help with pain and swelling. Prescription corticosteroids or cortisone shots might help. 
• Physical therapy: Exercises to strengthen the muscles around the knee and improve flexibility can help reduce symptoms and prevent the cyst from returning.
• Treat the underlying cause: Treating any underlying knee problem might help reduce the size of the cyst and the swelling or pain it causes. If there is an injury like a meniscus tear, treating this might also help treat the cyst.
• Needle aspiration: Your provider might use a needle to drain excess fluid from the cyst, providing temporary relief. 
• Surgery: In rare cases, if other treatments fail and the cyst continues to give you problems, arthroscopic surgery (a minimally invasive procedure using small instruments and a camera) might be needed to remove the cyst and repair any other issues. 

A Baker’s cyst can return, especially if the underlying cause isn’t treated or addressed. The best way to prevent a Baker cyst is to avoid knee injuries and treat underlying joint issues or chronic conditions.

To reduce the risk of a Baker’s cyst from returning, it’s important to:

• Follow the prescribed treatment plan for any underlying knee issues. Give your body time to rest and recover. 
• Maintain a healthy weight to reduce stress on your knee.
• Stretch and warm up before sports or working out. Cool down and stretch afterward.
• Strengthen the muscles around the knee with appropriate exercises.
• Avoid activities that strain the knee.