At high lumbar L1-L2, which muscle function is expected?

At high lumbar L1-L2, which muscle function is expected?

• A. Hip flexion
• B. Knee extension
• C. Ankle plantarflexion
• D. Elbow extension

Answer: (A)

At the L1–L2 level, the muscles most directly governed are those that move the hip, particularly the hip flexors. The iliopsoas, the prime hip flexor, is innervated mainly by L1–L2 (with L2 playing a key role). So hip flexion is the muscle action you’d expect to be controlled at this level. Knee extension relies mainly on the quadriceps, which are innervated by L2–L4; ankle plantarflexion depends on the posterior leg muscles innervated by S1–S2; elbow extension involves the cervical nerves (C7–C8) supplying the triceps. Because those functions are driven by nerves outside L1–L2, they aren’t the primary or most expected functions at this level.

At the L1–L2 level, the muscles most directly governed are those that move the hip, particularly the hip flexors. The iliopsoas, the prime hip flexor, is innervated mainly by L1–L2 (with L2 playing a key role). So hip flexion is the muscle action you’d expect to be controlled at this level.

Knee extension relies mainly on the quadriceps, which are innervated by L2–L4; ankle plantarflexion depends on the posterior leg muscles innervated by S1–S2; elbow extension involves the cervical nerves (C7–C8) supplying the triceps. Because those functions are driven by nerves outside L1–L2, they aren’t the primary or most expected functions at this level.