This is a real-world medical entrance exam question, please give the true answer based on the question and selection. Topic name: Thigh, Knee,Leg,Foot & Ankle injuries, Subject name: Orthopaedics
Which of the following structure is not a pa of knee extensor mechanism 
Select and explain. 
A. Quadriceps tendon, B. Biceps femoris, C. Tibial tubercle, D. Patella tendon
B: Biceps femoris
Answer: B: Biceps femoris 
Explanation: The biceps femoris is not pa of the extensor mechanism, but instead performs knee flexion. The other muscles are pa of the knee extensor mechanism.