What is a Baker’s cyst?

A Baker’s cyst, also known as a popliteal cyst or synovial cyst, is a soft, fluid-filled lump that forms on the back of your knee. Like many diseases and disorders, this cyst is named after the doctor who first described it. In the mid-1800s, Dr. William Morrant Baker concluded that these popliteal cysts resulted from fluid flowing out from a damaged knee joint. When structures in or around the joint are damaged, your knee produces extra fluid that can only flow one way so it forms a cyst on the back of your knee.

What causes a Baker’s cyst?

A Baker’s cyst is the result of joint damage that causes swelling in the knee. Examples of damage can include:

  • Arthritis (osteoarthritis or rheumatoid).
  • Direct damage to the knee (meniscus tear or ligament tear).
  • Inflammation.
  • Gout.

What are the symptoms of a Baker’s cyst?

Sometimes you’ll feel no pain at all, or only a slight pain with a Baker’s cyst. You may only have knee pain from the initial damage that caused the Baker’s cyst, but not the lump itself. Any strain can cause this lump or your knee to swell in size. When the knee or cyst swells, this can increase your pain and limit how much you can move your knee.

Symptoms of a Baker’s cyst may include:

  • A fluid-filled lump behind your knee.
  • Pain.
  • Stiffness of your knee.
  • Limited range of motion and ability to bend your knee.
  • Swelling of your knee and/or leg.

Sometimes, a Baker’s cyst can cause swelling and redness in your lower leg that can be similar to the symptoms of a blood clot. A blood clot is an emergency situation. If you are ever in doubt, reach out to your healthcare provider right away. Your provider can check out your symptoms and determine if it’s a Baker’s cyst or a blood clot.

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