This is a real-world medical entrance exam question, please give the true answer based on the question and selection. Topic name: None, Subject name: Surgery
[{'content': 'Joint LEAST involved in primary osteoahritis: March 2013 (b, h) \nSelect and explain. \nA. Hip, B. Trapezio-metacarpal, C. Knee, D. Coraco-clavicular', 'role': 'user'}, {'content': 'Answer: D \nExplanation: Ans. D i.e. Coracoclavicular Osteoahritis Usually OA involves: - Hip, - Knee Does not affect MCP joint Interphalangeal joints & nodes: - DIP - Heberdens node; PIP - Bouchard nodes X-ray shows: Osteophyte formation, narrowing of joint space etc.', 'role': 'assistant'}]