Physiological locking involves (DNB Dec 2012)
|A||Internal rotation of femur over stabilized tibia|
|B||Internal rotation of tibia over stabilized femur|
|C||External rotation of tibia over stabilized femur|
|D||External rotation of femur over stabilized tibia|
Internal rotation of femur over stabilized tibia
When the foot is fixed (tibia stabilized) the femur rotates medially to lock the knee.
This locking happens in the last 30 degree of extension and makes all the ligaments taut.
a. This locked position is very stable and keeps the lower limbs like 2 pillars.
b. Here the knee remains in full extension without much muscular efforts.
c. Knee locking is carried out by the same muscle which has carried out extension, i.e., quadriceps femoris.
Unlocking is carried out by the popliteus muscle, which moves femur laterally on stabilized tibia (fixed foot).
Unlocking is needed to initiate flexion at the knee before we start walking from the knee locked position.