Following an uneventful arthroscopic partial medial meniscectomy, a patient develops severe out-of-proportion pain, joint effusion, and significantly decreased range of motion on postoperative day 3. Joint aspiration yields turbid fluid with a white blood cell (WBC) count of 65,000 cells/mm³ and 90% polymorphonuclear leukocytes (PMNs). What is the most appropriate next step in management?

Explanation:
The patient's clinical presentation and synovial fluid analysis (WBC > 50,000/mm³ with >75% PMNs) are highly suspicious for acute post-arthroscopy septic arthritis. Septic arthritis is an orthopaedic surgical emergency. The standard of care requires urgent arthroscopic or open irrigation and debridement of the joint to reduce the bacterial load and remove purulent material, followed by targeted intravenous antibiotics. Delaying surgical intervention can lead to rapid and irreversible chondrolysis and joint destruction. Reference: Miller's Review of Orthopaedics, 8th Edition.