Prosthetic Joint Infection — SCE Rheumatology MCQ

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ModerateRheumatology EmergenciesProsthetic Joint InfectionSCE Rheumatology

A 55-year-old man presents 14 days after a primary total knee replacement with rapidly worsening knee pain. The knee has a tense effusion, warmth, swelling and markedly painful restriction of passive movement. His temperature is 38.5°C. The surgical wound is clean and dry, and there is no calf swelling. Which diagnosis must be prioritised and urgently excluded?

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Correct answer: C — Prosthetic joint infection

Prosthetic joint infection is the diagnosis that must be urgently excluded. Fever, a hot tense effusion and severe pain on passive movement only 14 days after arthroplasty indicate an acute deep joint process, even when the wound appears normal. This requires urgent orthopaedic-led assessment and appropriate microbiological sampling. Deep-vein thrombosis usually produces calf or diffuse limb swelling rather than an acutely inflamed intra-articular effusion. Wound cellulitis causes superficial erythema and tenderness, which are absent here. Haemarthrosis can cause a tense painful effusion but does not usually cause fever. Acute crystal arthritis may be triggered by surgery and can closely mimic infection; crystals also do not exclude concomitant infection, so prosthetic joint infection remains the priority diagnosis.

Reference: Royal National Orthopaedic Hospital NHS Trust. A Patient's Guide to Bone Infection Surgery, section 'What is a Joint Infection?'. Accessed 26 August 2026. https://www.rnoh.nhs.uk/patients-and-visitors/patient-information-guides/bone-infection-surgery