Branches of posterior part of lumbar plexus

Branches of the Posterior Part of Lumbar Plexus

The dorsal divisions of the anterior rami of lumbar spinal nerves, which form the posterior portion of the lumbar plexus, give rise to two major branches. These branches, both of which emerge from the lateral border of the psoas major muscle, include the following:

1. Lateral Femoral Cutaneous Nerve

• Origin: Formed by the dorsal divisions of the anterior rami of L2–L3.

• Course: The lateral femoral cutaneous nerve emerges from the lateral border of the psoas major muscle. It descends obliquely downwards across the iliacus muscle. The nerve runs posterior to the inguinal ligament, entering the thigh just medial to the anterior superior iliac spine (ASIS).

• Supplied Structures: It provides sensation to the skin over the anterior and posterior aspects of the lateral thigh, extending as far inferiorly as the knee.

2. Femoral Nerve

• Origin: Formed by the dorsal divisions of the anterior rami of L2–L4.

• Course: The femoral nerve emerges from the lower lateral border of the psoas major muscle. It descends laterally on the anterior surface of the iliacus muscle, deep to the iliacus fascia. This nerve passes beneath the inguinal ligament, lateral to the femoral artery, to enter the anterior compartment of the thigh.

• Supplied Structures: (Sensory): Provides sensation to the skin on the anterior surface of the thigh, medial side of the leg and foot, as well as the hip and knee joints. (Motor): Supplies the iliacus, pectineus, sartorius, rectus femoris, vastus medialis, vastus intermedius, and vastus lateralis muscles.