L3 myotome tests which movement?

L3 myotome tests which movement?

• A. Knee extension
• B. Hip flexion
• C. Elbow extension and wrist flexion
• D. Finger abduction and adduction

Answer: (B)

Hip flexion is tested by the L3 myotome because the iliopsoas, the main hip flexor, is primarily innervated by the L1–L3 nerve roots. In a typical exam, you ask the person to lift the thigh toward the chest (hip flexion), sometimes with resistance to gauge strength. This movement most directly reflects the integrity of the L3 root. If hip flexion is weak, it points to L3 involvement. The other movements shown involve different nerve roots (for example, knee extension involves a different lower-limb root, and upper-extremity movements involve cervical roots), so hip flexion best targets the L3 myotome.

Hip flexion is tested by the L3 myotome because the iliopsoas, the main hip flexor, is primarily innervated by the L1–L3 nerve roots. In a typical exam, you ask the person to lift the thigh toward the chest (hip flexion), sometimes with resistance to gauge strength. This movement most directly reflects the integrity of the L3 root. If hip flexion is weak, it points to L3 involvement. The other movements shown involve different nerve roots (for example, knee extension involves a different lower-limb root, and upper-extremity movements involve cervical roots), so hip flexion best targets the L3 myotome.