The S2 myotome is associated with which movements?

The S2 myotome is associated with which movements?

• A. Knee flexion and hip extension
• B. Ankle plantarflexion and eversion
• C. Knee extension and hip abduction
• D. Ankle dorsiflexion and inversion

Answer: (A)

This item tests which movements are controlled by the S2 nerve root, as defined by the myotome map. S2 contributes to both knee flexion and hip extension because it innervates the hamstrings (knee flexion) and the gluteus maximus (hip extension). So when you assess the S2 myotome, you’re looking for strength in bending the knee against resistance and in extending the hip against resistance. In practical testing, this would involve resisted knee flexion (curling the leg) and resisted hip extension (lifting the thigh backward while the person lies prone). Movements like ankle plantarflexion with eversion are mainly S1, ankle dorsiflexion with inversion involves L4–L5, and knee extension with hip abduction involves L3–L4 or L4–L5, so those do not reflect S2.

This item tests which movements are controlled by the S2 nerve root, as defined by the myotome map. S2 contributes to both knee flexion and hip extension because it innervates the hamstrings (knee flexion) and the gluteus maximus (hip extension). So when you assess the S2 myotome, you’re looking for strength in bending the knee against resistance and in extending the hip against resistance. In practical testing, this would involve resisted knee flexion (curling the leg) and resisted hip extension (lifting the thigh backward while the person lies prone). Movements like ankle plantarflexion with eversion are mainly S1, ankle dorsiflexion with inversion involves L4–L5, and knee extension with hip abduction involves L3–L4 or L4–L5, so those do not reflect S2.