Overview

A Baker's cyst is a fluid-filled cyst that causes a bulge and a feeling of tightness behind your knee. The pain can get worse when you fully flex or extend your knee or when you're active.

A Baker's cyst, also called a popliteal (pop-luh-TEE-ul) cyst, is usually the result of a problem with your knee joint, such as arthritis or a cartilage tear. Both conditions can cause your knee to produce too much fluid, which can lead to a Baker's cyst.

Although a Baker's cyst may cause swelling and make you uncomfortable, treating the probable underlying problem usually provides relief.

Source: http://www.mayoclinic.com

Symptoms

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

• Swelling behind your knee, and sometimes in your leg
• Knee pain
• Stiffness and inability to fully flex the knee

Your symptoms may be worse after you've been active or if you've been standing for a long time.

When to see a doctor

If you have pain and swelling behind your knee, see your doctor. Though unlikely, a bulge behind your knee may be a sign of a condition more serious than a fluid-filled cyst.

Source: http://www.mayoclinic.com

Causes

A lubricating fluid called synovial (sih-NO-vee-ul) fluid helps your leg swing smoothly and reduces friction between the moving parts of your knee.

But sometimes the knee produces too much synovial fluid, resulting in buildup of fluid in an area on the back of your knee (popliteal bursa), causing a Baker's cyst. This can happen because of:

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

Source: http://www.mayoclinic.com

Diagnosis

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, aneurysm or tumor, your doctor may order noninvasive imaging tests, including:

• Ultrasound
• X-ray
• Magnetic resonance imaging (MRI)

Source: http://www.mayoclinic.com

Complications

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

• Sharp pain in your knee
• Swelling in the calf
• 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 to rule out a more serious cause of your symptoms.

Lifestyle and home remedies

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:

• Follow the R.I.C.E. principles. These letters stand for rest, ice, compression and elevation. Rest your leg. Ice your knee. Compress your knee with a wrap, sleeve or brace. And elevate your leg when possible, especially at night.
• Try over-the-counter pain-relieving medications. Drugs such as ibuprofen (Advil, Motrin IB, others), naproxen sodium (Aleve, others), acetaminophen (Tylenol, others) and aspirin can help relieve pain. Follow the dosing instructions on the package. Don't take more than the recommend dosage.
• Reduce 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 he or she may be able to suggest alternative forms of exercise you can do in the meantime.

Source: http://www.mayoclinic.com