Q. A 26-year-old man comes to the emergency department due to severe right knee pain and swelling for the past 24 hours. He has no recent injuries or significant medical conditions. He is married and works as a high school teacher. The patient drinks 1-2 cans of beer daily; he smokes one pack per day but does not use recreational drugs. Temperature is 37.9 degrees Celsius (100.2 degrees Fahrenheit), blood pressure is 121/70 mmHg, and pulse is 84/min. The left knee is swollen, erythematous, warm, and tender on examination. Both active and passive range of motion is limited and painful. The remainder of the examination is unremarkable. The laboratory exam shows: ## Blood WBC: 13,250/mm3 * Neutrophils 74% * Lymphocytes 21% * Monocytes 4% ESR: 42mm/h CRP: 1.8 mg/dL ## Synovial fluid Color: Yellow Clarity: Opaque Viscosity: Low WBC 32,000/mm3 with 80% neutrophils Crystal: negative Gram stain: Positive for Gram-positive cocci What is the best emergency management for him?