The knee locking mechanisms in a closed kinetic chain

Question 1

Describe the knee locking mechanism in standing knee extension.

Answer 1

Knee joint is locked in closed pack position
Joint surfaces are more congruent
Femoral medial rotation and extension tightens ligaments.
Popliteus initiates ‘unlocking’ mechanism by laterally rotating femur on fixed tibia.

Question 2

Describe the knee locking mechanism in sitting to standing movement.

Answer 2

Locking into closed pack position
Femoral condyles ROLL anteriorly over tibial condyles.
Femoral condyles GLIDE posteriorly over tibial condyles (stops femoral condyles from rolling off tibial condyles)
Shorter lateral femoral condyle movement stops first
Femur medially rotates (SPINS) around fixed lateral condyle to complete the movement.

Question 3

Describe the knee UNlocking mechanism in standing to sitting movement.

Answer 3

Unlocking knee joint into open packed position (flexion)
Femur rotates(SPINS) laterally on the tibia
Femoral condyles ROLL posteriorly on the tibial condyles (relatively fixed)
Femoral condyles GLIDE anteriorly on the tibial condyles.

Question 4

Why is it important for the femoral condyles to glide anteriorly on the tibial condyles during open packed position?

Answer 4

It stops femoral condyles from rolling off the tibial condyles.