Anatomy Guide › Lower limb
Femoral Nerve
The femoral nerve is the reason you can stand up from a chair, climb a stair, and kick a ball. Formed from the second, third, and fourth lumbar nerve roots deep in the abdomen, it emerges through the psoas muscle, passes under the inguinal ligament at the groin, and promptly fans out into branches — most importantly to the quadriceps, the four-headed muscle mass that straightens the knee.
Its position at the groin is worth picturing: nerve, artery, and vein cross under the ligament side by side, nerve outermost (the mnemonic NAVY — nerve, artery, vein, Y-fronts — has taught the order to generations of students). This is also where clinicians find it, injecting local anesthetic around it as a femoral nerve block, a mainstay of pain control for hip fractures and knee surgery that can replace opioid doses with a single targeted numbing.
The femoral nerve also carries sensation from the front of the thigh, and — through its longest branch, the saphenous nerve — from the inner calf all the way to the ankle, the one part of the lower leg not handled by the sciatic system. Damage to the nerve, whether from pelvic surgery, a hematoma in the iliopsoas muscle, or diabetic neuropathy, announces itself characteristically: the knee buckles on stairs, the knee-jerk reflex fades, and the front of the thigh goes numb.
In Anamo, the femoral nerve threads the front-inner lane of the thigh alongside the femoral vessels, with the psoas above and the quadriceps below. If rectus femoris guesses run hot but aren't the answer, the nerve serving it is often the deeper truth.
- Drives the quadriceps — no femoral nerve, no straightened knee
- Passes the groin beside the femoral artery and vein (the 'NAVY' order)
- Femoral nerve blocks are standard pain control for hip fractures
- Its saphenous branch feels the inner calf down to the ankle
Think you could find the femoral nerve on a 3D model? Play Anamo and test yourself — every guess is color-coded by how close it lands to the mystery structure.