This is a real-world medical entrance exam question, please give the true answer based on the question and selection. Topic name: Lower limb, Subject name: Anatomy
Locking muscle of Knee joint is 
Select and explain. 
A. Vastus Lateralis, B. Vastus Medialis, C. Vastus Intermedius, D. Rectus Femoris
B: Vastus Medialis
Answer: B: Vastus Medialis 
Explanation: Locking is a mechanism that allows the knee to remain in the position of full extension as in standing without much muscular effoLocking occurs as a result of medial rotation of the femur during the last stage of extension. Vastus medialis prevents lateral displacement of the patella.Reference: Chaurasia Volume II; 7th edition; Page no: 169