This is a real-world medical entrance exam question, please give the true answer based on the question and selection. Topic name: Arthritis, Subject name: Orthopaedics
[{'content': 'Which is the most common joint involved in thalassemia? \nSelect and explain. \nA. Hip, B. Knee, C. Shoulder, D. Ankle', 'role': 'user'}, {'content': 'Answer: B \nExplanation: Ans. B. Knee* Most common joint involved in thalassemia is Knee joint.* Most common orthopedic symptom in thalassemia is leg pain.', 'role': 'assistant'}]