You are answering a USMLE-style medical question. Question: A 55-year-old man presents to a rheumatologist with bilateral wrist and knee pain that has been present for the last 10 years. The patient was a professional athlete who retired at age 50. He also notes morning stiffness in his joints that lasts approx. 50 minutes. He denies joint swelling, color changes in his digits, dryness of mucous membranes, and constitutional symptoms such as fever and chills. On physical exam, the physician notes several non-tender nodules on the left 1st, 3rd, and 4th distal interphalangeal joints. There is also tenderness with palpation at the base of both thumbs. The patient’s knees are enlarged, bilaterally, and he has pain and crepitus on passive range of motion. Which of the following is the most likely diagnosis? Options: A) Ankylosing spondylitis B) Gout C) Osteoarthritis D) Fibromyalgia Reply with ONLY the letter of the correct answer (A, B, C, or D). No explanation.