Femoral Nerve (L2–L4)
The largest branch of the lumbar plexus, the femoral nerve, is the primary nerve of the anterior compartment of the thigh.
Anatomy & Innervation
- Course: Emerges from the lateral border of the psoas major, passes deep to the inguinal ligament into the femoral triangle (lateral to the femoral artery).
- Motor: Innervates the quadriceps femoris (rectus femoris, vastus lateralis, vastus medialis, vastus intermedius), sartorius, and pectineus.
- Sensory: Supplies the anterior thigh and the medial aspect of the leg/foot via the saphenous nerve.
Clinical Significance
| Finding | Description |
|---|---|
| Injury Symptoms | Weakness in knee extension; loss of patellar reflex; sensory loss over the anterior thigh and medial leg. |
| Nerve Block | Commonly performed in the femoral triangle for anesthesia of the lower limb (e.g., knee surgery). |
High-Yield Exam Pearl:
The saphenous nerve is the only purely sensory branch of the femoral nerve that extends below the knee. It is frequently injured during saphenous vein harvesting (for coronary artery bypass grafting), leading to persistent numbness along the medial aspect of the lower leg.