Lumbar Plexus: Anatomy & Clinical Pearls

Iliohypogastric nerve — Root origins

L1 (±T12), superior branch.

Iliohypogastric nerve — Motor innervations

Internal oblique and transversus abdominis muscles.

Iliohypogastric nerve — Sensory distribution

Lateral gluteal region, lateral hip, and hypogastric region.

Ilioinguinal nerve — Root origins

L1 (inferior branch).

Ilioinguinal nerve — Motor innervations

Internal oblique and transversus abdominis muscles.

Ilioinguinal nerve — Sensory distribution

Medial proximal thigh (inguinal region) and immediate suprapubic region.

Genitofemoral nerve — Root origins

L1-L2.

Genitofemoral nerve — Motor innervations

Cremaster muscle in males (via genital branch).

Genitofemoral nerve — Sensory distribution

Scrotum/labia majora (genital branch) and proximal anterior thigh (femoral branch).

Lateral Femoral Cutaneous nerve — Root origins & course

L2-L3; passes under/through inguinal ligament near ASIS to lateral thigh.

Lateral Femoral Cutaneous nerve — Sensory distribution

Skin of the anterolateral thigh.

Femoral nerve — Root origins

L2-L4.

Femoral nerve — Motor distribution

Anterior thigh: iliacus, sartorius, quadriceps femoris, articularis genu, pectineus (part).

Femoral nerve — Sensory distribution

Anteromedial thigh, medial knee, and medial leg/foot (via saphenous nerve).

Obturator nerve — Root origins

L2-L4.

Obturator nerve — Motor distribution

Medial thigh: adductor longus/brevis/magnus, gracilis, obturator externus, pectineus (accessory branch).

Obturator nerve — Sensory distribution

Medial thigh, just proximal to the knee.

Meralgia paresthetica

Compression of lateral femoral cutaneous nerve causing burning/tingling in lateral thigh.

Femoral nerve injury — Clinical signs

Loss of knee extension, weak hip flexion, and absent patellar reflex.

Obturator nerve injury — Clinical signs

Impaired hip adduction and a wide-based gait.

Ilioinguinal / Iliohypogastric injury — Clinical presentation

Numbness in the suprapubic and inguinal regions, often post-abdominal surgery.

Genitofemoral neuralgia — Clinical presentation

Post-hernia repair pain radiating to the groin or anterior thigh.