During midstance, the external knee extension moment may create a tendency toward what if excessive?

During midstance, the external knee extension moment may create a tendency toward what if excessive?

• A. Hyperextension
• B. Foot slap
• C. Jackknifing
• D. Toe drag

Answer: (A)

During midstance, the ground reaction force line often acts behind the knee, producing an external knee extension moment that tends to straighten the knee. If this external extension moment becomes excessive, the knee can pass beyond neutral and move into hyperextension (genu recurvatum). This puts strain on posterior knee structures and can destabilize the joint. The other phenomena listed are associated with different phases or different mechanics—foot slap relates to early stance control, jackknifing to sagittal plane collapse, and toe drag to insufficient toe clearance in swing—so they don’t describe what happens with an excessive external knee extension moment during midstance.

During midstance, the ground reaction force line often acts behind the knee, producing an external knee extension moment that tends to straighten the knee. If this external extension moment becomes excessive, the knee can pass beyond neutral and move into hyperextension (genu recurvatum). This puts strain on posterior knee structures and can destabilize the joint. The other phenomena listed are associated with different phases or different mechanics—foot slap relates to early stance control, jackknifing to sagittal plane collapse, and toe drag to insufficient toe clearance in swing—so they don’t describe what happens with an excessive external knee extension moment during midstance.