L4 myotome tests which motion?

L4 myotome tests which motion?

• A. Hip abduction
• B. Shoulder elevation
• C. Ankle dorsiflexion
• D. Finger flexion

Answer: (C)

Testing the L4 myotome centers on ankle dorsiflexion. The key muscle here is the tibialis anterior, the primary mover for lifting the front of the foot, and its nerve supply includes the L4 root. When you ask a patient to dorsiflex against resistance, you’re directly evaluating the function of that L4-innervated muscle. If dorsiflexion is weak, it points to an issue at or near the L4 level, whereas normal dorsiflexion suggests intact L4 function. The other motions are controlled largely by different nerve roots or regions: hip abduction mainly involves the gluteal muscles (not isolated to L4), shoulder elevation is a C5-innervated movement, and finger flexion tests more caudal cervical roots (C8–T1). So ankle dorsiflexion best reflects the L4 myotome.

Testing the L4 myotome centers on ankle dorsiflexion. The key muscle here is the tibialis anterior, the primary mover for lifting the front of the foot, and its nerve supply includes the L4 root. When you ask a patient to dorsiflex against resistance, you’re directly evaluating the function of that L4-innervated muscle. If dorsiflexion is weak, it points to an issue at or near the L4 level, whereas normal dorsiflexion suggests intact L4 function.

The other motions are controlled largely by different nerve roots or regions: hip abduction mainly involves the gluteal muscles (not isolated to L4), shoulder elevation is a C5-innervated movement, and finger flexion tests more caudal cervical roots (C8–T1). So ankle dorsiflexion best reflects the L4 myotome.