Which movement does the L4 myotome test?

Which movement does the L4 myotome test?

• A. Ankle dorsiflexion
• B. Great toe extension and hip abduction
• C. Knee extension
• D. Shoulder elevation

Answer: (A)

Ankle dorsiflexion is what the L4 myotome tests. This movement is produced mainly by the tibialis anterior, so during the exam you ask the patient to lift the front of the foot toward the shin against your resistance while stabilizing the leg. Strong dorsiflexion indicates intact L4 motor function, while weakness suggests L4 involvement. For context, different myotomes map to different movements: great toe extension corresponds to L5, knee extension to L3–L4 (quadriceps), and shoulder elevation to cervical roots around C5.

Ankle dorsiflexion is what the L4 myotome tests. This movement is produced mainly by the tibialis anterior, so during the exam you ask the patient to lift the front of the foot toward the shin against your resistance while stabilizing the leg. Strong dorsiflexion indicates intact L4 motor function, while weakness suggests L4 involvement. For context, different myotomes map to different movements: great toe extension corresponds to L5, knee extension to L3–L4 (quadriceps), and shoulder elevation to cervical roots around C5.