Locking of the knee joint is caused by the contraction of:

Ans. D. Quadriceps femorisLocking of the knee happens during the last stages of extension when a person is standing up. Medial rotation of femur occurs during locking movement. This movement is aided by oblique pull of the ligaments of the knee joint and contraction of the quadriceps muscles. The ligaments are pulled taut when the knee joint is locked in place during standing. When the knee is flexed, it is unlocked by the popliteus muscle through the lateral rotation of femur.