Physiological locking involves
A i.e. Internal rotation of femur over stabilized tibia Physiological locking occurs in last 30 degree of extension, when femur rotates medially (internally) over stabilized tibiaQ. This very stable position is caused by quadriceps femoris muscle. Unlocking needed to initiate flexion is carried out by popliteus muscle, which moves femur laterally on stabilized tibia.
Internal rotation of femur over stabilized tibia
Internal rotation of tibia over stabilized femur
External rotation of tibia over stabilized femur
External rotation of femur over stabilized tibia