During terminal stance and pre-swing, the ground reaction force is located far anterior to the ankle axis.

During terminal stance and pre-swing, the ground reaction force is located far anterior to the ankle axis.

• A. Far anterior to the axis
• B. Posterior to the axis
• C. Directly through the axis
• D. Medial only

Answer: (A)

The key idea is that where the ground reaction force passes relative to a joint’s axis determines the direction and presence of the joint moment. In terminal stance and pre-swing, the body weight shifts toward the forefoot, moving the line of action of the ground reaction force far in front of the ankle joint axis. This anterior lever arm creates a plantarflexion moment at the ankle, which helps power the push-off and forward progression of gait. If the force were behind the ankle axis, it would tend to create a dorsiflexion moment and resist push-off. If it went directly through the axis, there would be little or no moment at the ankle. Therefore, being far anterior to the ankle axis best explains the mechanics of late stance and the transition into swing.

The key idea is that where the ground reaction force passes relative to a joint’s axis determines the direction and presence of the joint moment. In terminal stance and pre-swing, the body weight shifts toward the forefoot, moving the line of action of the ground reaction force far in front of the ankle joint axis. This anterior lever arm creates a plantarflexion moment at the ankle, which helps power the push-off and forward progression of gait.

If the force were behind the ankle axis, it would tend to create a dorsiflexion moment and resist push-off. If it went directly through the axis, there would be little or no moment at the ankle. Therefore, being far anterior to the ankle axis best explains the mechanics of late stance and the transition into swing.