Lateral femoral cutaneous nerve

At a glance

English

Lateral femoral cutaneous nerve

Latin (TA2)

Nervus cutaneus lateralis femoris

System

Nerve

Region

Lower limb

Side

Paired, left and right

About the lateral femoral cutaneous nerve

Sometimes called the thigh's lateral cutaneous nerve, this nerve carries skin sensation only and has no motor fibres. It is built from the posterior divisions of the L2 and L3 ventral rami within the lumbar plexus.

It appears at the outer edge of psoas major, about halfway down that muscle and below the ilioinguinal nerve, and then runs obliquely across the front of iliacus beneath the iliac fascia, aiming for the anterior superior iliac spine. On the right it lies behind the caecum and on the left behind the descending colon. It leaves the pelvis under or through the outer end of the inguinal ligament, usually a little medial to the spine, passing through the muscular compartment beneath the ligament. In the thigh it crosses in front of or through sartorius and splits into front and back branches.

The front branch comes through the fascia lata roughly a hand's breadth below the inguinal ligament and spreads over the anterolateral thigh down to the knee. Its final twigs join cutaneous twigs of the femoral nerve and the saphenous nerve's infrapatellar branch, forming a fine network around the kneecap, the peripatellar plexus. The back branch pierces the fascia lata higher up and fans backwards over the outer and rear aspects of the thigh, from about the greater trochanter to roughly mid-thigh.

The sharp angle the nerve makes as it leaves the pelvis beside the iliac spine leaves it open to compression. The result, meralgia paraesthetica (Bernhardt-Roth syndrome), is burning, tingling or numbness over the outer thigh with no weakness. Tight belts or clothing, obesity, prolonged standing, seat belts, diabetes and surgery near the iliac crest, such as bone graft harvesting or hip approaches, are recognised causes. Most cases settle once the pressure is removed; a local anaesthetic injection beside the spine helps confirm the diagnosis and ease the pain, and surgical release is kept for stubborn cases.

Course and supply

Arises from

Posterior divisions of the L2 and L3 ventral rami; appears at the outer border of psoas major.

Ends in

Passes under the outer inguinal ligament close to the anterior superior iliac spine, then ends as front and back branches in the skin of the anterolateral and lateral thigh.

Supplies

Purely sensory to the skin of the front and outer thigh down to the knee, and the lateral upper thigh below the greater trochanter.