Knee Muscles contributing to the same function Contents FLEXION Biceps Femoris Semitendinosus Semimembranosus Sartorius Gracilis Gastrocnemius Plantaris Popliteus EXTENSION Rectus Femoris Vastus Lateralis Vastus Medialis Vastus Intermedius Tensor Fascia Latae (secondary function) Gluteus Maximus (secondary function) LATERAL ROTATION Biceps Femoris (secondary function) Popliteus (secondary function) MEDIAL ROTATION Semimembranosus (secondary function) Semitendinosus (secondary function) Popliteus Sartorius (secondary function) Gracilis (secondary function)