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: Orthopaedics
[{'content': 'The most common site of primary osteoarthrosis is - \nSelect and explain. \nA. Hip joint, B. Knee joint, C. Ankle joint, D. Shoulder joint', 'role': 'user'}, {'content': 'Answer: B \nExplanation: In general, weight bearing lower limb joints are affected more commonly than upper limb joints.\nHowever, No textbook has mentioned which is the commonest joint : knee or hip.\nAccording to me it is knee because of following facts :-\n\n\nI have seen hardly one or two cases of primary OA of hip; while, I have seen hundreds of cases of Primary OA of knee in my OPD. At least 4 to 5 patients of primary OA of knee comes daily to my OPD.\n"OA commonly affects the knee joint"\xa0\xa0 —Ebnezar\n"OA of hip is second in frequency to the knee joint" —Ebnezar', 'role': 'assistant'}]