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Crystal arthritis — SCE Rheumatology MCQ

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ModerateMusculoskeletal investigationsCrystal arthritisSCE Rheumatology

A 52-year-old woman has an acutely swollen knee after diuretic treatment. Examination shows the joint is warm with a moderate effusion. Investigations show inflammatory markers are raised. The consultant wants the next test most likely to confirm the suspected process or guide treatment. The result will change diagnosis, staging or immediate treatment. What is the most appropriate investigation?

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Correct answer: B — Ultrasound-guided aspiration

Ultrasound-guided aspiration is the best answer because ultrasound-guided aspiration is the investigation most likely to resolve the immediate diagnostic or monitoring question in crystal arthritis. Complement and anti-dsDNA is a plausible distractor, but it does not account for the key discriminator in the stem. ENA profile and CT angiography would be more appropriate in a different clinical pattern or at another point in the pathway, while MRI scan is suboptimal for this presentation. Clinical pearl: autoantibodies are supportive tests and should be interpreted alongside phenotype, inflammatory markers, urinalysis and imaging.

Reference: BSR hot swollen joint guideline; NICE NG100; EULAR imaging recommendations