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Septic arthritis — RCPSC EM MCQ

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ModerateMusculoskeletalSeptic arthritisRCPSC EM

A 71-year-old with diabetes presents with acute atraumatic knee pain, fever 38.5°C, inability to bear weight, and a large effusion. X-ray shows degenerative change without fracture. What is the most appropriate investigation?

Educational content. Not a substitute for clinical judgement or local policy.

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Correct answer: E — Urgent arthrocentesis for cell count, Gram stain, culture and crystal analysis

Septic arthritis cannot be excluded by X-ray or serum markers; synovial fluid analysis is the key diagnostic test.

Reference: Canadian orthopaedic and emergency medicine septic arthritis practice