Baker's cyst

Baker's cyst

Definition:

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-LIT-e-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.


Symptoms:

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

Your symptoms may be worse after you've been active, or even if you've just been standing for a long time.
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 rather than a fluid-filled cyst.

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

Complications:


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 to rule out a more serious cause of your symptoms.

Treatments and drugs:

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:

• 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.

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.

Baker's cysts associated with osteoarthritis may stay swollen even if you're receiving arthritis treatment. You and your doctor may discuss surgery to remove the cyst if it doesn't resolve and it affects your joint movement. Baker's cyst removal may be an option for a cyst that repeatedly refills after you have it drained with a needle.