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In some cases, a Baker's cyst causes no pain, and you may not even notice it. If you do experience signs and symptoms, you may notice:

• Swelling behind your knee, and sometimes in your leg
• Knee pain
• Stiffness
• Texture similar to a balloon filled with water

When to see a doctor
If you're experiencing pain and swelling behind your knee, see your doctor to determine the cause. Though unlikely, a bulge behind your knee may be a sign of a more serious condition, such as a tumor or a popliteal artery aneurysm, rather than a fluid-filled cyst.

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The cartilage and tendons in your knee rely on a lubricating fluid called synovial (si-NO-vee-ul) fluid. This fluid helps your leg swing smoothly and reduces friction between the moving parts of your knee.

Synovial fluid circulates throughout your knee and passes in and out of various tissue pouches (bursae) throughout your knee. A valve-like system exists between your knee joint and the bursa on the back of your knee (popliteal bursa). This regulates the amount of synovial fluid going in and out of the bursa.

But sometimes the knee produces too much synovial fluid, resulting in buildup of fluid in the bursa and what is called a Baker's cyst. This can be caused by:

• Inflammation of the knee joint, such as occurs with various types of arthritis
• Knee injury, such as a cartilage tear

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Rarely, a Baker's cyst bursts and synovial fluid leaks into the calf region causing:

• Sharp pain in your knee
• Swelling
• Sometimes, redness of your calf or a feeling of water running down your calf

These signs and symptoms closely resemble those of a blood clot in a vein in your leg. If you have swelling and redness of your calf, you'll need prompt medical evaluation.

©1998-2012 Mayo Foundation for Medical Education and Research (MFMER). Terms of use.
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You're likely to first see your family doctor or a general practitioner. However, you may then be referred to a doctor who specializes in disorders affecting the bones, joints and muscles (an orthopedist or orthopedic surgeon, rheumatologist, or physical medicine and rehabilitation specialist).

Because appointments can be brief, and there's often a lot of ground to cover, it's a good idea to arrive well prepared. Here's some information to help you get ready for your appointment, and what to expect from your doctor.

What you can do

• Write down any symptoms you're experiencing, including any that may seem unrelated to the reason for which you scheduled the appointment.
• Write down key personal information, including recent life changes.
• Make a list of all medications, vitamins and supplements that you're taking.
• Write down questions to ask your doctor.

Your time with your doctor may be limited, so preparing a list of questions can help you make the most of your time together. List your questions from most important to least important in case time runs out. For a Baker's cyst, some basic questions to ask your doctor include:

• What caused this cyst to develop?
• What kinds of tests do I need? Do these tests require any special preparation?
• Is a Baker's cyst temporary or long lasting?
• What treatments are available, and which do you recommend?
• What types of side effects can I expect from treatment?
• What steps can I take on my own that might help?
• Do I need to limit my activity? If so, how much? And, for how long?
• I have another health condition. How can I best manage these conditions together?

In addition to the questions that you've prepared to ask your doctor, don't hesitate to ask questions during your appointment anytime you don't understand something.

What to expect from your doctor
Your doctor is likely to ask you a number of questions, such as:

• When did you first begin experiencing symptoms?
• Do you feel pain or stiffness all the time, or does the pain come and go with activity?
• Does your knee swell, feel unstable or lock?
• How severe are your symptoms?
• Does anything seem to improve your symptoms?
• What, if anything, appears to worsen your symptoms?

What you can do in the meantime
If the cyst isn't causing you pain, you may not need to do anything prior to seeing your doctor. However, if the cyst is causing symptoms, such as pain and stiffness, taking the following steps may help:

• Use a cold pack or ice wrapped in a protective covering to ice the affected area when it's bothering you.
• Rest your affected knee and keep the leg elevated whenever possible.
• Take an over-the-counter pain-relieving medication to ease your symptoms. Nonsteroidal anti-inflammatory medications (NSAIDs) — such as aspirin, ibuprofen (Advil, Motrin, others) and naproxen (Aleve, others) — can reduce pain and inflammation, while acetaminophen (Tylenol, others) can ease pain.
• Use a knee sleeve or brace for compression.

©1998-2012 Mayo Foundation for Medical Education and Research (MFMER). Terms of use.
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A Baker's cyst can often be diagnosed with a physical exam. However, because some of the signs and symptoms of a Baker's cyst mimic those of more serious conditions, such as a blood clot or tumor, your doctor may order noninvasive imagine tests, including:

• Ultrasound
• Magnetic resonance imaging (MRI)

©1998-2012 Mayo Foundation for Medical Education and Research (MFMER). Terms of use.
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Many times, no treatment is required and a Baker's cyst will disappear on its own.

If the cyst is very large and causes a lot of pain, your doctor may use the following treatments:

• Physical therapy. Icing, a compression wrap and crutches may help reduce pain and swelling. Gentle range-of-motion and strengthening exercises for the muscles around your knee also may help to reduce your symptoms and preserve knee function.
• Fluid drainage. Your doctor may drain the fluid from the knee joint using a needle. This is called needle aspiration and is often performed under ultrasound guidance.
• Medication. Your doctor may inject a corticosteroid medication, such as cortisone, into your knee to reduce inflammation. This may relieve pain, but it doesn't always prevent recurrence of the cyst.

Typically though, doctors treat the underlying cause rather than the Baker's cyst itself.

If your doctor determines that a cartilage tear is causing the overproduction of synovial fluid, he or she may recommend surgery to remove or repair the torn cartilage.

In some instances, particularly if you have osteoarthritis, the cyst may not go away even after your doctor treats the underlying cause. If the cyst doesn't get better, causes pain and interferes with your ability to bend your knee, or if — in spite of aspirations — fluid in the cyst recurs and hinders knee function, you may need to be evaluated for surgery to remove the cyst.

©1998-2012 Mayo Foundation for Medical Education and Research (MFMER). Terms of use.
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If your doctor determines that arthritis is causing the cyst, he or she may advise you to take some or all of the following steps to reduce the inflammation and lessen the production of synovial fluid:

• Follow the P.R.I.C.E. principles. These letters stand for protection, rest, ice, compression and elevation. Protect your leg by using crutches to take the weight off the knee joint and to allow pain-free walking. Rest your leg. Ice the inflamed area. Compress your knee with a wrap, sleeve or brace. And elevate your leg when possible, especially at night.
• Try nonsteroidal anti-inflammatory drugs (NSAIDs) or acetaminophen. NSAIDs, such as aspirin, ibuprofen (Advil, Motrin, others), naproxen (Aleve, others) and similar drugs, can help relieve pain, as can acetaminophen (Tylenol, others). Prescription NSAIDs can provide higher doses and greater potency than over-the-counter NSAIDs.
• Scale back your physical activity. Doing so will reduce irritation of your knee joint. Your doctor can offer you guidance on how long you need to reduce your activity levels, and may be able to suggest alternative forms of exercise you can do in the meantime.

©1998-2012 Mayo Foundation for Medical Education and Research (MFMER). Terms of use.
Read this article on Mayoclinic.com.