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Prosthetic joint infection — ABIM Board MCQ

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HardInfectious DiseaseProsthetic joint infectionABIM Board

A 72-year-old has an 18-month-old knee arthroplasty with new pain and swelling. ESR and CRP are elevated, radiographs show no fracture, there is no sinus tract, and she is clinically stable. What is the next diagnostic step?

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Correct answer: D — Perform pre-antibiotic arthrocentesis with cell count and cultures

The best answer is “Perform pre-antibiotic arthrocentesis with cell count and cultures”. A painful prosthesis with unexplained elevated inflammatory markers warrants diagnostic arthrocentesis. Synovial leukocyte analysis and cultures establish whether infection is likely and identify an organism. In a stable patient, antibiotics should be withheld until sampling to improve culture yield. No sinus tract does not exclude PJI, and serum or advanced imaging alone is insufficient.

Reference: IDSA Prosthetic Joint Infection Guideline: https://www.idsociety.org/practice-guideline/prosthetic-joint-infection/