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Suspected native-joint septic arthritis with concurrent crystal arthritis — MRCEM SBA MCQ

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HardInfection and sepsisSuspected native-joint septic arthritis with concurrent crystal arthritisMRCEM SBA

A 68-year-old man with established gout and type 2 diabetes presents with 24 hours of severe left knee pain. The knee is hot and swollen, and passive movement is markedly painful. He cannot bear weight. His temperature is 38.7°C, pulse 106/min and blood pressure 126/74 mmHg; C-reactive protein is 186 mg/L. Blood cultures have been taken. Knee aspiration yields turbid fluid containing monosodium urate crystals; no organisms are seen on the initial Gram stain, and synovial culture is pending. He has not received antibiotics. What is the most appropriate management plan now?

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

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Correct answer: A — Begin empirical intravenous antibiotics and request urgent orthopaedic assessment for joint drainage.

This is a suspected septic native knee despite the finding of urate crystals: gout and septic arthritis can coexist. Fever, inability to bear weight, a severely painful restricted joint and substantial inflammation warrant urgent assessment rather than attribution of the presentation to gout alone. NICE advises immediate referral when septic arthritis is suspected. ([rightdecisions.scot.nhs.uk](https://www.rightdecisions.scot.nhs.uk/nhs-tayside-refguide/medicine/rheumatology/gout/?UNLID=22638775202621594927)) A negative initial Gram stain does not resolve the uncertainty; a UK-and-Ireland multicentre study found that it missed many microbiologically positive cases. ([pubmed.ncbi.nlm.nih.gov](https://pubmed.ncbi.nlm.nih.gov/40330095/?utm_source=openai)) Blood cultures and joint fluid have already been obtained, so begin empirical intravenous treatment now, admit the patient and involve orthopaedics urgently to assess drainage. UK NHS guidance supports sampling before antibiotics where feasible, alongside antimicrobial treatment and source control. ([rightdecisions.scot.nhs.uk](https://www.rightdecisions.scot.nhs.uk/antimicrobial-prescribing-nhs-lothian/body-systems/bone-and-joint-infections/septic-arthritis/?utm_source=openai)) B gives antibiotics but delays assessment of the infected joint until culture returns. C responds to the crystals but leaves suspected infection untreated. D risks injecting steroid into a potentially infected joint and delays referral. E recognises the need for drainage but unnecessarily postpones antibiotics for further samples when blood cultures and a diagnostic aspirate have already been collected.

Reference: NICE NG219: Gout—diagnosis and management, recommendations 1.1.3–1.1.4 (9 June 2022) — https://www.nice.org.uk/guidance/ng219/chapter/Recommendations NHS Tayside RefGuide: Gout (Reviewed 1 May 2025) — https://www.rightdecisions.scot.nhs.uk/nhs-tayside-refguide/medicine/rheumatology/gout/?UNLID=22638775202621594927 Multi-centre evaluation of Gram stain in the diagnosis of septic arthritis (2025) — https://pubmed.ncbi.nlm.nih.gov/40330095/