Which spinal segments form the femoral nerve?

The femoral nerve (n. femoralis) is formed from the anterior rami of spinal nerves L₂–L₄ as part of the lumbar plexus.

Through which anatomical structure does the femoral nerve enter the thigh?

The femoral nerve enters the thigh through the muscular lacuna (lacuna musculorum).

What is the spatial relationship between the femoral nerve and vessels in the femoral triangle?

In the femoral triangle, the femoral nerve lies lateral to the femoral artery and vein.

Which branch of the femoral nerve accompanies the vessels down to the leg?

The longest branch of the femoral nerve, the saphenous nerve (n. saphenus), accompanies the vessels.

Femoral Nerve: Anatomy, Branches, and Innervation (USMLE)

Femoral Nerve

n. femoralis

For medical students2 min readUpdated 2026-10-10

The femoral nerve (n. femoralis) is a major nerve of the lumbar plexus, formed by the anterior rami of spinal nerves L₂–L₄. It enters the thigh through the muscular lacuna, lying lateral to the femoral vessels. It innervates the quadriceps femoris, sartorius, and iliopsoas muscles, and provides sensory innervation to the anterior thigh, medial leg, and medial border of the foot.

Spinal segmentsL₂–L₄ (lumbar plexus)

Topographic exitMuscular lacuna (*lacuna musculorum*)

Position in the thighIn the femoral triangle, it lies lateral to the femoral vessels

Anatomy and Formation of the Femoral Nerve

The femoral nerve (n. femoralis) arises from the anterior rami of spinal nerves L₂–L₄ as part of the lumbar plexus (plexus lumbalis). It enters the thigh by passing through the muscular lacuna (lacuna musculorum), which is separated from the vascular lacuna by the iliopectineal arch (arcus iliopectineus). Within the femoral triangle, the n. femoralis lies lateral to the femoral vessels (a. et v. femorales), separated from them by the fascia of the iliopsoas muscle.

Branches of the Femoral Nerve

Shortly after entering the thigh, the femoral nerve divides into multiple branches:

Muscular branches — supply the heads of the quadriceps femoris muscle and the pectineus muscle (m. pectineus).
Anterior cutaneous branches (rr. cutanei anteriores) — pierce the fascia lata along the medial margin of the sartorius muscle (m. sartorius) to supply the skin of the anterior thigh.
Saphenous nerve (n. saphenus) — the longest branch of the femoral nerve, which accompanies the femoral vessels through the adductor canal, emerges on the leg, and innervates the skin of the medial leg and the medial border of the foot.

What Does the Femoral Nerve Innervate?

The nerve provides motor and sensory innervation to the following structures:

Muscles: the heads of the quadriceps femoris, the iliopsoas (hip flexion and medial rotation), the sartorius (m. sartorius), and contributes to the dual innervation of the pectineus muscle (m. pectineus).
Skin: anterior surface of the thigh (rr. cutanei anteriores) and the medial leg along with the medial border of the foot (n. saphenus).

Additionally, the knee-jerk reflex (patellar reflex) tests the integrity of the femoral nerve and spinal segments L₂–L₄.

Relations in the Subinguinal Region

In the lacunae inferior to the inguinal ligament, the n. femoralis runs lateral to the vascular bundle. The muscular lacuna (lacuna musculorum) transmits the n. femoralis, the iliopsoas muscle (m. iliopsoas), and the lateral femoral cutaneous nerve (n. cutaneus femoris lateralis). Medially, the vascular lacuna (lacuna vasorum) transmits the femoral artery and vein, along with the femoral branch of the genitofemoral nerve (r. femoralis n. genitofemoralis).

Frequently asked questions

Which spinal segments form the femoral nerve?: The femoral nerve (n. femoralis) is formed from the anterior rami of spinal nerves L₂–L₄ as part of the lumbar plexus.
Through which anatomical structure does the femoral nerve enter the thigh?: The femoral nerve enters the thigh through the muscular lacuna (lacuna musculorum).
What is the spatial relationship between the femoral nerve and vessels in the femoral triangle?: In the femoral triangle, the femoral nerve lies lateral to the femoral artery and vein.
Which branch of the femoral nerve accompanies the vessels down to the leg?: The longest branch of the femoral nerve, the saphenous nerve (n. saphenus), accompanies the vessels.

Go deeper

Lumbar plexus (plexus lumbalis)
Muscular lacuna (lacuna musculorum)
Femoral triangle
Adductor canal (canalis adductorius)
Saphenous nerve (n. saphenus)