During loading response, the combined external moments at the ankle, knee, and hip threaten to do what to the limb?

During loading response, the combined external moments at the ankle, knee, and hip threaten to do what to the limb?

• A. Lift it into swing
• B. Fully extend it
• C. Rotate it externally
• D. Collapse it

Answer: (D)

During loading response the leg must accept body weight and stay stable as the opposite leg advances. The ground reaction force creates external torques at the ankle, knee, and hip that would drive these joints into a more flexed posture. If those external moments aren’t opposed, the limb would buckle under the load—essentially collapsing. The muscles around these joints must eccentrically counteract these external forces to keep the limb upright and controlled as weight is transferred forward. That’s why the correct idea is that the external moments threaten to collapse the limb.

During loading response the leg must accept body weight and stay stable as the opposite leg advances. The ground reaction force creates external torques at the ankle, knee, and hip that would drive these joints into a more flexed posture. If those external moments aren’t opposed, the limb would buckle under the load—essentially collapsing. The muscles around these joints must eccentrically counteract these external forces to keep the limb upright and controlled as weight is transferred forward. That’s why the correct idea is that the external moments threaten to collapse the limb.