skip to main content

Suspected septic arthritis of the ankle — MSRA MCQ

Instant feedback + full explanation. One question, done properly.

HardAnkle and FootSuspected septic arthritis of the ankleMSRA

A 64-year-old man presents with a 20-hour history of rapidly worsening pain, swelling and erythema of his right ankle. He has had 2 previous crystal-proven gout flares affecting the first MTP joint. He has type 2 diabetes and takes prednisolone 7.5 mg daily for polymyalgia rheumatica. Nine days ago, he received an ultrasound-guided intra-articular methylprednisolone injection into the right ankle for osteoarthritis. He is afebrile and systemically well. The ankle is diffusely hot, swollen and exquisitely painful; active and passive movement are markedly restricted and he cannot weight-bear. There is no skin ulcer, cellulitis, penetrating injury or calf swelling. CRP is 11 mg/L and white cell count is normal. What is the most appropriate management today?

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

Reveal the answer and explanation

Correct answer: A — Refer immediately via the local septic arthritis pathway for hospital assessment and diagnostic joint aspiration

Explanation lettering: E = shown as A · A = shown as B · D = shown as C · C = shown as D · B = shown as E

This is suspected septic arthritis until proved otherwise. The decisive features are an acutely inflamed monoarthritis with severe restriction of passive as well as active movement and inability to weight-bear, occurring shortly after an intra-articular corticosteroid injection. Diabetes and long-term systemic corticosteroid treatment further increase susceptibility to infection. Previous crystal-proven gout makes gout plausible, but does not safely explain away a possible septic joint. Absence of fever, a normal white cell count and a low CRP do not exclude early septic arthritis, particularly in an immunosuppressed patient. NICE advises assessment for septic arthritis in anyone presenting with a painful, red, swollen joint and immediate referral through the local pathway when it is suspected. Hospital assessment permits urgent synovial fluid aspiration for microscopy, crystal analysis and culture, with subsequent antimicrobial and drainage decisions. A delays definitive assessment and ultrasound cannot exclude joint infection. B is attractive because of the prior gout history, but treating presumed gout risks delaying management of septic arthritis. C is inappropriate because the presentation is of intra-articular inflammation rather than cellulitis, and oral treatment may delay appropriate aspiration and treatment. D is unsafe because blood tests should not determine whether a clinically suspected septic joint is referred.

Reference: NICE NG219: Gout: diagnosis and management — Recommendations (2022) — https://www.nice.org.uk/guidance/ng219/chapter/Recommendations Intra-articular procedures and associated septic arthritis: A mini-review (2025) — https://pubmed.ncbi.nlm.nih.gov/39798919/ Evidence-based diagnostics: adult septic arthritis (2011) — https://pubmed.ncbi.nlm.nih.gov/21843213/