11th June 2024

A 24-year-old man presents to the hospital with fevers and right knee pain for the past 4 days

A 24-year-old man presents to the hospital with fevers and right knee pain for the past 4 days. He denies any cough, dysuria or abdominal pain at present. Past medical history is unremarkable. He has been in a monogamous relationship for 6 months, but prior to that, he had multiple male and female sexual partners. On examination, his temperature is 38.5C, pulse 115/min, RR 18/min and BP 115/76mmHg. The right knee is warm to touch, erythematous and tender with a moderate effusion. Aspiration of the joint shows WCC of 70,000/mm3 (90% neutrophils). Gram stain and microscopy were negative for organisms and no crystals were seen.

Which investigation is most likely to lead to a diagnosis?

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