USMLE® Step 1 style questions USMLE
A 47-year-old man comes to the office because of a 1-week history of right knee pain and limited lower limb movement. His medical history is relevant to previous knee trauma and a recently diagnosed rheumatoid arthritis. The patient currently works as a football coach. Physical examination shows well-circumscribed swelling, tenderness, and increased volume in the posterior region of the right knee and limited 90-degree angle extension/in flexion of his right knee. Additionally, the increased volume in the right knee posterior region disappears with a 45-degree flexion. His temperature is 36.4°C (97.5°F), pulse is 80/min, respirations are 14/min, blood pressure is 110/60 mmHg. Which of the following is the most likely cause of this patient's condition?