Femoral Nerve

Original Editor - Mandeepa Kumawat

Top Contributors - Lucinda hampton, Mandeepa Kumawat, Kirenga Bamurange Liliane, Naomi O'Reilly, Vidya Acharya, Khloud Shreif, Joao Costa, Kim Jackson and Eric Henderson

Introduction

The femoral nerve is the largest nerve of the lumbar plexus. It originates from the dorsal divisions of the L2-L4 ventral rami.  It has a role in motor and sensory processing in the lower limbs. It controls:

1. The major hip flexor muscles, as well as knee extension muscles.
2. Sensation over the anterior and medial thigh, as well as medial leg down to the hallux (great toe).

Image 1 and 2: Femoral nerve and muscle innervations

Anatomy

 In the Pelvis

• The nerve emerges from behind the psoas muscle to run laterally, deep to the iliac fascia above the iliacus muscle.
• Muscular branches are first given off to the psoas and then to the iliacus muscles (sometimes known together as the iliopsoas muscle) before the nerve runs beneath the inguinal ligament.

It then enters the thigh

• It begins lateral to the femoral artery (behind the inguinal ligament), dividing approximately 4 cm below the inguinal ligament into anterior and posterior divisions.
• 
  The anterior division gives rise to the medial and intermediate cutaneous nerves of the thigh and muscular branches to the sartorius and pectineus muscles.
• The posterior division supplies the four heads of the quadriceps femoris (vastus medialis, vastus lateralis, vastus intermedius and rectus femoris)and then continues along the medial border of the calf as the saphenous nerve.
• The saphenous nerve is the largest and longest branch of the femoral nerve and supplies the skin over the medial side of the leg.

Articular Supply

• The femoral nerve also innervates the capsule of the hip joint and allows for proprioceptive feedback about the joint.
• The knee joint is supplied by the nerves to the three vasti. The nerve to the vastus medialis contains numerous proprioceptive fibres from the knee joint, accounting for the thickness of the nerve.

Note: The lateral thigh is not supplied by the femoral nerve but is innervated by the lateral femoral cutaneous nerve , which is derived directly from the lumbar plexus, receiving innervation from the L2–L3 nerve roots.

Femoral Triangle

The following structures pass through the femoral triangle:

• Femoral nerve - Which innervates the anterior compartment of the thigh
• Femoral sheath containing: Femoral artery and branches - Arterial supply for majority of the lower limb; Femoral vein - The great saphenous vein drains into the femoral vein within the triangle; Femoral canal - Contains lymph nodes and vessels

Physiotherapy Relevance

Femoral nerve damage (also referred to as femoral nerve dysfunction or neuropathy), can occur from an injury or prolonged compression. Typically, damage and dysfunction of the femoral nerve are associated with the leg weakness and sensation changes.

Image 3: Casualty, suffering from a gunshot wound to the groin.

Injury

Injury of the femoral is uncommon but may be injured by a stab, gunshot wounds, or a pelvic fracture. The femoral nerve can be damaged during penetrating trauma to the thigh. It can also be damaged during hip replacement operations, particularly the anterior approach (not commonly used) where the nerve can be stretched and damaged. Listed here are the characteristic clinical features:

Motor loss

• Poor flexion of the hip, because of paralysis of the iliacus, psoas and sartorius muscles.
• Inability to extend the knee, because of paralysis of the quadriceps femoris.

Sensory impairment

• Sensory decline over the anterior and medial aspects of the thigh, as a result of engagement of the intermediate and lateral cutaneous nerves of the thigh.
• Sensory loss on the medial side of the leg and foot up to the ball of the great toe (first metatarsophalangeal joint), because of engagement of the saphenous nerve.

Apart from direct injury aside the femoral nerve damage can be caused by a number of other factors.

• Certain medical conditions eg diabetes, can damage this nerve due to impaired metabolic functioning, and is common.
• Other mediating factors include fracturing the pelvis, internal bleeding, or oxygen deprivation to the nerve due to becoming encased in a tumor or being subjected to pressure by the presence of a tumor.

Image 3: Casualty, suffering from a gunshot wound to the groin.

Other relevant issues

• Patellar tendon reflex: The femoral nerve is responsible for the patellar tendon reflex (tests L3-L4 spinal component
• Femoral nerve block: Femoral nerve block (in combination with sciatic nerve block) may be indicated in patients requiring lower limb surgery who cannot tolerate a general anaesthetic. A femoral nerve block can also be used as peri- and post-operative analgesia for patients with a fractured neck of femur who cannot tolerate particular analgesics.
• Femoral nerve tension test

Viewing

Below is a 6 minute video on the femoral nerve.