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Common Septic Arthritis exam questions for medical finals, OSCEs and MRCP PACES


Question 1.

What are common organisms causing septic arthritis?

  • Staph aureus
  • Streptococci
  • Neisseria gonorrhoeae (in the sexually active)
  • Haemophilus (in children, but rare due to vaccination)
  • The elderly and people with chronically inflamed joints are prone to infection with unusual organisms.
  • Lyme disease (Borellia burgdorferi) can cause an inflammatory arthritis


Question 2.

What investigations should be done in suspected septic arthritis?

  • Bloods (especially for WCC, CRP and ESR)
  • Blood cultures
  • Aspirate joint and
    • Send the fluid for URGENT microscopy, culture and crystals
    • Gram stain positive in only 50%, synovial fluid growth positive in 90%
    • MUST be done prior to starting antibiotics
  • Swabs from skin wounds and the throat, sputum and urine
  • Joint X-ray (baseline)