If the posterior stop allows only slight plantarflexion (~5°), knee motion results?

If the posterior stop allows only slight plantarflexion (~5°), knee motion results?

• A. Knee flexion
• B. Knee extension
• C. Knee buckling
• D. Recurvatum

Answer: (B)

Limit­ing plantarflexion with a posterior stop changes how the ankle-knee complex moves during stance. The gastrocnemius spans both joints and uses ankle plantarflexion to help induce knee flexion as the limb accepts weight and progresses forward. When plantarflexion is limited to about 5 degrees, the ankle can’t move into the plantarflexed position effectively, so the knee doesn’t receive the usual flexion moment. As a result, the knee stays more extended rather than flexing, giving knee extension as the motion outcome.

Limit­ing plantarflexion with a posterior stop changes how the ankle-knee complex moves during stance. The gastrocnemius spans both joints and uses ankle plantarflexion to help induce knee flexion as the limb accepts weight and progresses forward. When plantarflexion is limited to about 5 degrees, the ankle can’t move into the plantarflexed position effectively, so the knee doesn’t receive the usual flexion moment. As a result, the knee stays more extended rather than flexing, giving knee extension as the motion outcome.