The femoral nerve is a mixed nerve of the lower limb that innervates the muscles and skin of the hip and thigh. The femoral nerve originates from the lumbar plexus, arising from the anterior rami of spinal nerves L2-L4. In fact, it is the longest branch of the lumbar plexus.
The femoral nerve is split by the lateral circumflex femoral artery into an anterior and posterior division. These divisions give rise to motor and sensory branches:
- The motor branches of the femoral nerve are the nerve to pectineus, nerve to sartorius and muscular branches to the quadriceps femoris. They innervate the flexors of the hip (pectineus, iliacus, sartorius) and the extensors of the knee (quadriceps femoris).
- The sensory branches of the femoral nerve are the medial femoral cutaneous nerve of thigh, intermediate femoral cutaneous nerve of thigh and the saphenous nerve, which is the terminal branch of the femoral nerve. These nerves innervate the skin of the anteromedial thigh and medial aspects of the knee, leg and foot.
In this article, we will discuss the anatomy and function of the femoral nerve.
|Lumbar plexus (L2-L4)
Motor: Nerve to pectineus, nerve to sartorius, muscular branches
Sensory: Medial femoral cutaneous nerve of thigh, intermediate femoral cutaneous nerve of thigh, saphenous nerve
|- Flexors of the hip: pectineus, iliacus, sartorius
- Extensors of the knee: quadriceps femoris
- Skin of anteromedial thigh, skin of medial leg and foot
- Origin and course
- Branches and innervation
Origin and course
The femoral nerve is the largest branch of the lumbar plexus. It arises from the posterior cords of the lumbar plexus (L2-L4) and provides motor innervation to the anterior thigh muscles. This is in contrast to the obturator nerve, which arises from the anterior cords (L2-L4) and supplies the medial compartment of the thigh.
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The femoral nerve emerges from the lower lateral border of the psoas major. It descends beneath the midpoint of the inguinal ligament to enter the femoral triangle, coursing lateral to the femoral artery and vein.
You can use the mnemonic NAVY to remember the content order of the femoral triangle, from lateral to medial:
- lYmphatics (femoral canal)
Once it passes beneath the inguinal ligament, it divides into an anterior (superficial) and a posterior (deep) division. The anterior division branches into the medial cutaneous and intermediate cutaneous nerve of the thigh and provides branches to the sartorius muscle. The posterior division supplies the quadriceps femoris musle. The femoral nerve terminates as the saphenous nerve in the gaiter region of the leg.
Learn more about the lumbar plexus branches here:
Branches and innervation
The femoral nerve gives off several motor branches:
- The first, are small branches that arise in the abdomen and supply the iliacus muscle.
- The nerve to pectineus branches off the medial aspect of the femoral nerve close to the inguinal ligament to innervate the pectineus, a small muscle in the medial compartment of the thigh.
- The nerve to sartorius branches from the anterior division of the femoral nerve to supply the sartorius muscle (the tailor’s muscle).
- The muscular branches arise from the posterior division and supply the four heads of the quadriceps femoris (vastus medialis, vastus lateralis, vastus intermedius and rectus femoris).
The anterior division of the femoral nerve gives rise to the medial femoral cutaneous nerve of thigh and intermediate femoral cutaneous nerve of thigh. These nerves supply sensation to the skin over the anterior and medial region of the thigh.
The saphenous nerve forms the terminal branch of the femoral nerve and is also the longest nerve in the body. It descends into the adductor canal along with the femoral vessels. However, the nerve does not enter the adductor hiatus. Instead, it emerges on the medial side of the knee to supply sensation to the skin over the region of the greater saphenous vein in the gaiter region.
In addition to providing cutaneous innervation, the femoral nerve also provides articular branches that innervate the capsules of the hip and knee joints, and allow for proprioceptive feedback about the joints.
Try out our quiz to test your knowledge about the supply of the lower extremity:
Femoral nerve damage
The femoral triangle is formed by the lateral border of adductor longus, the medial border of sartorius and the inguinal ligament (with pectineus and illiopsoas forming the floor). It contains, from lateral to medial, the femoral nerve, artery and vein.
The femoral artery can be palpated 1 cm below the mid inguinal point (mid-way from the pubic symphysis to the anterior superior iliac spine or ASIS).
This is different to the mid point of the inguinal ligament (mid-way between the pubic tubercle and the ASIS). The femoral nerve can be damaged during penetrating trauma to the thigh. It can also be damaged during hip operations, particularly the anterior approach (not commonly used) where the nerve can be stretched and damaged. The fibres of the femoral nerve also mediate the knee reflex.
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