Knee Infection

A knee joint infection, also called septic arthritis, is rare but needs immediate medical attention to prevent permanent damage to the joint. Attend A&E or your local walk in centre.


A joint infection will present with a sudden onset of a red, hot and swollen knee without trauma. As there is an infection you will usually feel generally unwell and may have a fever.

You may be more prone to a joint infection:

  • Following bacterial infection elsewhere in the body
  • After surgery such as a knee or hip replacement
  • If you have a long term condition such as diabetes or rheumatoid arthritis
  • If you are on medication to suppress your immune system
  • If you use injected drugs
  • if you have recently injured the joint


  • You may have a blood test or fluid aspirated from the knee with a needle. This will look for signs of inflammation or infection and the bacteria involved.


  • Septic arthritis is treated with intravenous antibiotics ( directly into the vein).
  • You will normally need to stay in hospital whilst being treated with intravenous antibiotics
  •  You may need to be on bed rest for a few days to reduce pressure on the knee.
  • You may need to have fluid removed from the joint by a syringe and in some cases keyhole surgery (arthroscopy)
  • You will be given pain relief medication
  • After you finish the intravenous antibiotics you will normally need to continue with antibiotic tablets for at least a month at home
  • Most people do completely recover but some people experience persistent stiffness in the knee.

Useful Link – detailed information about septic arthritis