A 40-year-old man presents with acute onset of a hot, swollen knee joint with severe pain and limited movement. He is febrile at 38.7 °C. What is the most appropriate immediate investigation/management step?AStart NSAIDs and review in a weekBArrange urgent arthrocentesis for Gram stain, culture and crystals, and start empiric IV antibiotics if septic arthritis suspectedCOrder MRI of the knee and delay treatment until results are backDStart high-dose oral steroids without aspirationEDischarge with rest and ice packs onlyCheck my answer