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': 'Which activity will be difficult to perform for a patient with an anterior cruciate deficient knee joint- \nSelect and explain. \nA. Walk downhill, B. Walk uphill, C. Sit cross leg, D. Getting up from sitting', 'role': 'user'}, {'content': 'Answer: A \nExplanation: It has been explained that ACL is taut in extension, and prevent anterior gliding of tibia an femur. When one walks downhill, he tries to keep the knee in extension to maintain the balance and In extension, ACL is required to prevent anterior gliding of tibia. Therefore a person with ACL deficient knee will have difficulty in going downhill.\nOpposite is true for PCL. When one climbs upstairs, he keeps the knee in flexion most of the time. PCL is taut in flexion and prevent posterior gliding of tibia. Therefore PCL deficient knee will have difficulty in climbing upstairs.', 'role': 'assistant'}]