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Popliteal cyst information

Patient information A-Z

Your ultrasound today confirms that you have a popliteal cyst.


  • A popliteal cyst, also referred to as a Baker’s cyst, is a swelling filled with synovial fluid (joint fluid) that forms behind the knee.
  • A popliteal cyst usually develops when the knee is damaged and excess joint fluid is produced.
  • The excess fluid leads to an increase in pressure that causes a bulge in the lining of the joint out into the back of the knee forming a popliteal cyst.
  • Common conditions such as rheumatoid arthritis and osteoarthritis are often associated with a popliteal cyst. Sometimes no cause for the formation of the cyst can be found.

What are the symptoms?

  • The size and amount of swelling produced by a popliteal cyst varies.
  • A small cyst may give no symptoms; large cysts usually produce more problems
  • Symptoms include:
    • Discomfort or pain behind the knee
    • Tightness that increases on standing
    • Difficulty in bending the knee.
  • Sometimes the cyst will burst causing pain and swelling behind the knee and down the calf muscle. When this occurs the cyst gives symptoms similar to that of a deep vein thrombosis.

What treatment is available?

Often the symptoms will resolve without any treatment.

  • It is important to keep as mobile as possible.
  • Elevating the leg may help to reduce the swelling.
  • The pain and inflammation can be helped by using over the counter antiinflammatory medication. Please check with your GP that there are no contraindications if you have not taken these before.
  • If symptoms do not improve it is important to see your GP. Your GP may wish to treat any underlying condition that may have contributed to the development of the cyst.

Source of information

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Cambridge University Hospitals
NHS Foundation Trust
Hills Road, Cambridge

Telephone +44 (0)1223 245151