Which motion causes the knee to unlock during the gait cycle?

Which motion causes the knee to unlock during the gait cycle?

• A. Supination of subtalar joint
• B. Plantarflexion at the ankle
• C. Pronation of subtalar joint
• D. Dorsiflexion at the ankle

Answer: (C)

Pronation at the subtalar joint drives internal rotation of the tibia, which unlocks the knee from its extended, “screwed-in” position during gait. When the foot pronates in stance, the leg internally rotates, allowing the knee to flex and absorb shock as weight is borne forward. Supplying external rotation (supination) would tend to keep the knee in that locked state, while ankle motions like plantarflexion or dorsiflexion don’t directly create the tibial rotation needed to unlock.

Pronation at the subtalar joint drives internal rotation of the tibia, which unlocks the knee from its extended, “screwed-in” position during gait. When the foot pronates in stance, the leg internally rotates, allowing the knee to flex and absorb shock as weight is borne forward. Supplying external rotation (supination) would tend to keep the knee in that locked state, while ankle motions like plantarflexion or dorsiflexion don’t directly create the tibial rotation needed to unlock.