Day 0 · 08:20ArrivalThe knee is swollen, hot, and exquisitely tender; he holds it in slight flexion and will not let the triage nurse straighten it. He feels feverish. No injury, no skin break he knows of. VitalsHR92BP146/84RR16SpO297%T37.9One investigation decides this case. Which?Joint aspiration, before any anti-inflammatory treatmentA serum urate level todayBlood cultures alone, before anything touches the joint tonightA plain radiograph of the knee in two views