This is a real-world medical entrance exam question, please give the true answer based on the question and selection. Topic name: Joints of Lower Extremity, Subject name: Anatomy
Flexion of knee joint is caused by - 
Select and explain. 
A. Rectusfemoris, B. Vastus medialis, C. Hamstrings, D. Vastus lateralis
C: Hamstrings
Answer: C: Hamstrings 
Explanation: Ans. is 'c' i.e., Hamstringso Hamstrings (semimembranosis, semitendinesus and biceps femoris) are felxors of knee,o Other three options are part of quadriceps an extensor of knee.Muscles producing movements at the knee jointMovementPrincipal musclesAccessory' musclesA. Flexion1. Biceps femoris2. Semitendinosus3. Semimembranosus1. Gracilis2. Sartorius3. PopliteusB. ExtensionQuadriceps femorisTensor fasciae lataeC. Medial rotation of flexed leg1. Popliteus2. Semimembranosus3. Semitendinosus1. Sartorius2. GracilisD. Lateral rotation of flexed legBiceps femoris--