The femoral nerve is a large nerve arising from the lumbar plexus and one of two major nerves supplying the lower limb.
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Gross anatomy
Origin
It arises from posterior divisions of L2-L4 roots of the lumbar plexus.
Course
It emerges from the lateral border of the psoas muscle at its inferior aspect, before descending in between the lateral border of the psoas and medial border of iliacus muscles. It sends a motor branch to iliacus before passing under the inguinal ligament to enter the femoral triangle.
Femoral triangle
lies above iliacus, outside and lateral to the femoral sheath
gives off the nerve to pectineus, just after crossing the inguinal ligament
divides into anterior (superficial) and posterior (deep) divisions, separated by the lateral femoral circumflex artery
the terminal branch of the deep division reaches the apex of the femoral triangle to become the saphenous nerve
Branches
Proximal branches
branches to iliacus muscle (prior to crossing inguinal ligament)
nerve to pectineus (immediately after crossing inguinal ligament)
Superficial division
Branches of the superficial division include:
nerve to sartorius
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anterior femoral cutaneous nerves, which consist of:
medial femoral cutaneous nerve
intermedial femoral cutaneous nerve
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 and articularis genu
nerve to vastus medialis: 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: fibers 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 knee 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)