Femoral nerve

The femoral nerve is a large nerve arising from the lumbar plexus and one of two major nerves supplying the lower limb.

Gross anatomy

Origin

It arises from posterior divisions of L2-L4 roots of the lumbar plexus.

Course

• emerges from the lateral border of the psoas muscle to descend between the iliacus and psoas muscles
• sends a motor branch to iliacus before passing under the inguinal ligament

Femoral triangle

• lies above iliacus, outside and lateral to the femoral sheath
• sends a branch to pectineus
• the lateral femoral circumflex artery separates the nerve into superficial and deep divisions
• the terminal branch of the deep division reaches the apex of the femoral triangle to become the saphenous nerve

See the article: femoral triangle

Branches

Superficial division

Branches of the superficial division include:

• the nerve to sartorius
• medial cutaneous nerve of thigh contributes to subsartorial plexus (with branches of the obturator and saphenous nerves)
• the intermediate cutaneous nerve of thigh
• sympathetic vasomotor supply to blood vessels

Deep division

Branches of the deep division include:

• nerve to rectus femoris: also receives articular supply from hip
• nerve to vastus lateralis: also receives articular supply from knee
• nerve to vastus intermedius
• nerve to vastus medius: also receives articular supply from knee
• continues as the saphenous nerve, which passes behind sartorius

Supply

The femoral nerve provides motor supply to the anterior compartment of the thigh and sensory supply to the hip, anterior and medial thigh, knee, and medial leg (as the saphenous nerve).

Variant anatomy

• femoral nerve splits into two or three separate slips within the psoas muscle but unites to descend as a single bundle ²
• accessory femoral nerve: fibres arise separately in lumbar plexus, passes anterior to femoral nerve, may terminate as saphenous nerve / cutaneous branch
• femoral branch replacing lateral femoral cutaneous nerve which usually branches directly off lumbar plexus
• saphenous nerve terminating  at knee with distribution replaced by branch of the tibial nerve

Related pathology

Femoral nerve is endangered by trauma. Injury results in weakness of thigh extension and numbness overlying the anterior/medial thigh and medial leg.

The femoral nerve is responsible for the patellar tendon reflex (tests L3-L4 spinal component)

• femoral nerve neuropathy