Locking and Unlocking Mechanism of Knee Joint

Question 1

What is the locking mechanism

Answer 1

It is a mechanism that allows the knee to remain in a position of full extension.

Question 2

What muscle is involved in the locking mechanism

Answer 2

Quadriceps femoris especially vastus medialis.
Its action is that it extends the knee.

Question 3

Locking occurs as a result of what

Answer 3

Medial rotation of femur and lateral rotation of tibia.

Question 4

Locking is aided by four ligaments , mention them

Answer 4

anterior cruciate ligament
oblique popliteal ligament
collateral ligaments.

Question 5

As the knee moves into full extension, what ligament is the first to become tense or taut

Answer 5

Anterior cruciate ligament.

Question 6

Further extebsion of medial condyle is made possible by

Answer 6

Passive rotation of the lateral condyle around radius of the tense ant cruciate ligament.

This gives it a longer and more curved articular surface than the lateral condyle.

Question 7

Lateral condyle serves as what

Answer 7

An axis around which medial condyle rotates backwards.

Question 8

The medial rotation of the femur on the tibia tightens the remaining 3 ligaments.What does this cause

Answer 8

It limits further rotation of the knee.

Question 9

This is said to be the screwhome movement and it causes the locking of the knee joint.

Question 10

What causes unlocking of the knee joint

Answer 10

Lateral rotation of femur
Medial rotation of tibia

Question 11

What muscle produces this action

Answer 11

Popliteus

Question 12

What needs to happen for the knee to be unlocked

Answer 12

Femur must be laterally rotated to produce flexion and this is done by the popliteus muscle.

Question 13

What happens in the flexed position

Answer 13

All four ligaments are relaxed.
Small part of femoral surface articulates with tibia

Question 14

Active rotation during flexion is produced by what muscles

Answer 14

Semimembranosus and semitendinosus medially.
Biceps femoris laterally.