skip to main content

Persistent native-knee septic arthritis after initial arthroscopic debridement — SCE Rheumatology MCQ

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

ModerateSeptic ArthritisPersistent native-knee septic arthritis after initial arthroscopic debridementSCE Rheumatology

A 58-year-old man with seropositive rheumatoid arthritis treated with methotrexate and adalimumab is admitted with acute septic arthritis of his native right knee. Arthroscopic irrigation and debridement are performed, and synovial fluid and blood cultures grow methicillin-susceptible Staphylococcus aureus. He receives intravenous flucloxacillin according to microbiology advice. Seventy-two hours after surgery, he remains febrile at 38.3°C with worsening knee pain and a recurrent tense effusion. His C-reactive protein has risen from 148 mg/L immediately after surgery to 186 mg/L. Repeat aspiration yields purulent fluid containing Gram-positive cocci; no new organism or antimicrobial resistance has been identified. He is haemodynamically stable and fit for further surgery. Which is the most appropriate next management step?

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

Reveal the answer and explanation

Correct answer: E — Arrange urgent repeat operative irrigation and debridement with further microbiological sampling, while continuing targeted intravenous therapy

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

This is early treatment failure after initial surgical debridement. The decisive features are persistent fever, worsening local symptoms, recurrent purulent effusion, a rising CRP and organisms still visible in synovial fluid despite appropriate organism-directed therapy. Together, these indicate inadequate source control rather than insufficient antimicrobial spectrum. Urgent orthopaedic reassessment and repeat operative irrigation and debridement are therefore required; further operative specimens should be obtained, and targeted intravenous flucloxacillin should continue. A is inappropriate because observation risks progressive cartilage damage when several concordant clinical, biochemical and synovial markers indicate failure. C is attractive in an immunosuppressed patient, but there is no evidence of resistance, polymicrobial infection or a new pathogen; broader antibiotics do not substitute for drainage. D may become useful to identify adjacent osteomyelitis, periarticular abscess or another deep focus, but imaging should not postpone repeat source control in a clearly reaccumulating infected joint. E can be considered as an initial drainage strategy in selected accessible joints or when operative risk is prohibitive, but this patient has failed operative treatment, remains fit for surgery and has objective persistent infection. Repeat debridement is commonly required: systematic-review evidence suggests initial surgical treatment fails in approximately one-quarter of adult native-joint cases.

Reference: Guideline for management of septic arthritis in native joints (SANJO) (12 January 2023) — https://pubmed.ncbi.nlm.nih.gov/36756304/ Failure rates in surgical treatment in adults with bacterial arthritis of a native joint: a systematic review of 8,586 native joints (2023) — https://pubmed.ncbi.nlm.nih.gov/37395855/ Management of septic arthritis in adults with a hot swollen joint: British Society for Rheumatology guideline scope (16 June 2025) — https://pubmed.ncbi.nlm.nih.gov/40524816/