This is a real-world medical entrance exam question, please give the true answer based on the question and selection. Topic name: Ohopaedics Q Bank, Subject name: Orthopaedics
[{'content': 'Triple deformity of knee is classically seen in: \nSelect and explain. \nA. Fracture patella, B. Tuberculosis, C. Rheumatic ahritis, D. Ankylosing spondylitis', 'role': 'user'}, {'content': 'Answer: B \nExplanation: Triple deformity is seen in tuberculosis of knee consists of ( Mnemonic PErF ):- P- Posterior subluxation of tibia Er- External rotation of leg F- Flexion at knee', 'role': 'assistant'}]