The S1 myotome is associated with which ankle movements?

• A. Dorsiflexion and inversion
• B. Plantarflexion and inversion
• C. Dorsiflexion and eversion
• D. Plantarflexion and eversion

Answer: (D)

The S1 myotome is tested by movements powered by the S1 nerve root: plantarflexion of the ankle and eversion of the foot. Plantarflexion is pointed toes downward, and eversion is turning the sole outward. The gastrocnemius-soleus complex mainly handles plantarflexion, while the fibularis (peroneus) muscles handle eversion; both sets are associated with S1. That combination—plantarflexion with eversion—best matches the S1 pattern. Dorsiflexion and inversion, or either movement paired with the other motion, point more toward other roots (like L4-L5), so they’re less consistent with S1.