What is a Baker’s cyst?

A Baker’s cyst is also known as a popliteal cyst or synovial cyst. It is a soft, fluid-filled lump that forms on the back of the knee. The lump is sometimes mistaken for a blood clot. A Baker’s cyst usually develops because of damage to the knee. When the structures in or around the joint are damaged, the knee produces more fluid.

What are the symptoms of a Baker’s cyst?

Sometimes there is only slight pain to signal a Baker’s cyst. There can still be pain in the knee from the initial damage that caused the Baker’s cyst. You may notice a soft lump that sticks out from the back of the knee. Any strain can cause this lump or the knee to swell in size.

It is possible for the Baker’s cyst to go away. The cyst can reduce in size on its own or burst under the skin. When the cyst bursts under the skin, the fluid is absorbed back into the body. It is often best to treat the source of the knee problem to get rid of the Baker’s cyst.

What causes a Baker’s cyst?

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

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

Last reviewed by a Cleveland Clinic medical professional on 10/25/2016.


  • Better Health Channel: Baker’s Cyst
  • Fritschy, D., Fasel, J., Imbert, JC. et al. The popliteal cyst. Knee Surg Sports Traumatol Arthr (2006) 14: 623-628
  • Koplas M; Schils J; Sundaram M. The painful knee: choosing the right imaging test. Cleve Clin J Med. 2008 May;75( 5):377-84

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