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 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.
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.
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:
- Magnetic resonance imaging (MRI)
Sometimes a Baker’s cyst will disappear on its own. However, if the cyst is large and causes pain, your doctor may recommend the following treatments:
- 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.
- 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.
- 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.
If possible, doctors treat the underlying cause of the cyst. 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.
Baker’s cysts associated with osteoarthritis usually improve with treatment of the arthritis. Surgical intervention is rarely needed.