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: Anatomy
[{'content': 'Locking of knee joint occurs due to - \nSelect and explain. \nA. Lateral rotation of femur during last degrees of extension., B. Medial rotation of femur during last degrees of extension, C. Lateral rotation of femur during last degrees of flexion, D. Medial rotation of femur during last degrees of flexion', 'role': 'user'}, {'content': 'Answer: B \nExplanation: During last stages of extension, femur rotates medially on tibia due to quadriceps femoris to lock the knee joint.', 'role': 'assistant'}]