During swing phase, knee motion is produced primarily by which mechanism?

During swing phase, knee motion is produced primarily by which mechanism?

• A. Maximal quadriceps contraction
• B. Soleus activity
• C. Tibialis posterior activation
• D. Passive forward momentum

Answer: (D)

Knee motion during swing is driven mainly by passive dynamics: gravity and the limb’s forward momentum. As the thigh is pulled forward by hip flexors, gravity helps the leg bend, so the knee flexes without needing strong active contraction from the quadriceps. Activating the quadriceps would actually extend the knee, not promote flexion, so maximal quadriceps activity isn’t how the knee moves in this phase. The ankle-related muscles (like the soleus) and foot-control muscles (like the tibialis posterior) influence foot placement rather than knee flexion. In late swing, the hamstrings may help decelerate motion to prepare for heel strike, but the primary knee flexion during swing comes from passive forward momentum and gravity.

Knee motion during swing is driven mainly by passive dynamics: gravity and the limb’s forward momentum. As the thigh is pulled forward by hip flexors, gravity helps the leg bend, so the knee flexes without needing strong active contraction from the quadriceps. Activating the quadriceps would actually extend the knee, not promote flexion, so maximal quadriceps activity isn’t how the knee moves in this phase. The ankle-related muscles (like the soleus) and foot-control muscles (like the tibialis posterior) influence foot placement rather than knee flexion. In late swing, the hamstrings may help decelerate motion to prepare for heel strike, but the primary knee flexion during swing comes from passive forward momentum and gravity.