During terminal stance and pre-swing, the ground reaction force is positioned relative to the knee joint axis.

During terminal stance and pre-swing, the ground reaction force is positioned relative to the knee joint axis.

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

Answer: (A)

During terminal stance and pre-swing, the line of action of the ground reaction force shifts behind the knee joint axis. This positioning creates an external knee extension moment, which helps the knee move toward full extension as the body prepares to push off. If the force were anterior to the axis, it would produce a knee flexion moment that would resist extension; if it passed directly through the axis, the external moment would be essentially zero and not contribute to knee motion; the idea of being “medial only” isn’t relevant to the sagittal knee moment in this context.

During terminal stance and pre-swing, the line of action of the ground reaction force shifts behind the knee joint axis. This positioning creates an external knee extension moment, which helps the knee move toward full extension as the body prepares to push off. If the force were anterior to the axis, it would produce a knee flexion moment that would resist extension; if it passed directly through the axis, the external moment would be essentially zero and not contribute to knee motion; the idea of being “medial only” isn’t relevant to the sagittal knee moment in this context.