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
Commonest dangerous complication of posterior dislocation of knee is - 
Select and explain. 
A. Popliteal artery injury, B. Sciatic nerve injury, C. Ischaemia of lower leg compartment, D. Femoral artery injury
A: Popliteal artery injury
Answer: A: Popliteal artery injury 
Explanation: Dislocation of the knee

This rare injury results from severe violence to the knee so that all of its supporting ligaments are torn.
It is a major damage to the joint, and is often associated with injury to the popliteal artery.
Treatment is by reduction followed by immobilization in a cylinder cast.