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Septic Arthritis — SCE Infectious Diseases MCQ

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EasyBone & Joint InfectionSeptic ArthritisSCE Infectious Diseases

A 50-year-old man presents with a painful swollen right knee 10 days after arthroscopic surgery. Aspirated synovial fluid shows 85,000 WCC/µL (95% neutrophils), no crystals, and Gram-positive cocci in clusters on Gram stain. What is the most appropriate initial management?

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Correct answer: C — Arthroscopic washout plus IV Flucloxacillin 2 g QDS

Acute septic arthritis post-surgery requires urgent surgical lavage (arthroscopic or open) and empirical IV antibiotics. Gram-positive cocci in clusters suggest Staphylococcus aureus. First-line empirical treatment is IV Flucloxacillin 2 g QDS (assuming MSSA until sensitivities confirm). Vancomycin is reserved for MRSA risk or penicillin allergy. Antibiotics alone without joint washout are inadequate. Rifampicin is used for prosthetic joint infections, not native joint septic arthritis in the acute setting.

Reference: NICE NG157 2024 – Septic arthritis; BSR 2023 – Guidelines on management of hot swollen joint