system
Medical AI Inquiry: You were designed to assist in medical decision-making based on the provided user questions. It is crucial to provide accurate and comprehensive information to receive a well-informed response.
user
A 51-year-old woman comes to the emergency department because of a 1-day history of severe pain in her left knee. To lose weight, she recently started jogging for 30 minutes a few times per week. She has type 2 diabetes mellitus and hypertension treated with metformin and chlorothiazide. Her sister has rheumatoid arthritis. She is sexually active with two partners and uses condoms inconsistently. On examination, her temperature is 38.5°C (101.3°F), pulse is 88/min, and blood pressure is 138/87 mm Hg. The left knee is swollen and tender to palpation with a significantly impaired range of motion. A 1.5-cm, painless ulcer is seen on the plantar surface of the left foot. Which of the following is most likely to help establish the diagnosis?
assistant
Perform arthrocentesis