A 32-year-old male presents with a 3-week history of progressive right knee pain and swelling. He recalls a puncture wound to the sole of his foot from a contaminated nail 6 weeks ago, which he ignored. On examination, the knee is warm, tender, and has restricted range of motion. Temperature is 38.2°C. X-ray of the knee shows periosteal reaction and cortical erosion of the distal femur. Blood culture grows Pseudomonas aeruginosa. What is the most likely diagnosis?