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Mnemonic

Knee Joint Movements and the Screw-Home Mechanism

A memory aid for the movements of the knee and how it locks.

Anatomy Lower Limb
Expansion

Flexion and extension, with rotation possible only when the knee is flexed

Expansion

  • Flexion and extension - the main hinge movements
  • Rotation - medial and lateral rotation of the tibia is only possible when the knee is flexed and unlocked

At full extension the tibia rotates laterally on the femur (the screw-home mechanism) to lock the knee for stable standing. Popliteus unlocks it to allow flexion.