If the quadriceps fail to control the external knee flexion moment during loading response, what may occur?

If the quadriceps fail to control the external knee flexion moment during loading response, what may occur?

• A. Foot slap
• B. Circumduction
• C. Hip hiking
• D. Knee buckling

Answer: (D)

During loading response, the ground reaction force creates an external knee flexion moment. The quadriceps must contract eccentrically to produce a knee extension moment that counters this force, helping to control knee bending and absorb impact. If the quadriceps fail to control that external flexion moment, the knee cannot remain stable in extension and tends to give way into flexion. This loss of stability is what we call knee buckling. Foot slap happens at heel strike due to poor dorsiflexion control, not knee moment control. Circumduction and hip hiking are swing-phase compensations used to clear the limb, not immediate responses to an unstable knee during loading response.

During loading response, the ground reaction force creates an external knee flexion moment. The quadriceps must contract eccentrically to produce a knee extension moment that counters this force, helping to control knee bending and absorb impact.

If the quadriceps fail to control that external flexion moment, the knee cannot remain stable in extension and tends to give way into flexion. This loss of stability is what we call knee buckling.

Foot slap happens at heel strike due to poor dorsiflexion control, not knee moment control. Circumduction and hip hiking are swing-phase compensations used to clear the limb, not immediate responses to an unstable knee during loading response.