The leg is supplied by the lumbar plexus (L1 to L4) at the front and the sacral plexus (L4 to S4) at the back. The sciatic nerve, the largest nerve in the body, carries most of the supply below the knee.
Femoral nerve
The femoral nerve passes under the inguinal ligament beside the femoral artery and straightens the knee through the quadriceps. Its saphenous branch gives sensation to the inner leg.
Obturator nerve
The obturator nerve runs through the pelvis to the inner thigh and pulls the legs together (hip adduction). It can be injured in pelvic fractures or pelvic surgery.
Sciatic nerve
The sciatic nerve leaves the pelvis deep in the buttock and bends the knee through the hamstrings. Gluteal injections use the ventrogluteal site to stay well away from it.
Tibial and common fibular nerves
Above the knee the sciatic nerve splits into the tibial nerve, which points the foot down and feels the sole, and the common fibular (peroneal) nerve, which lifts the foot and toes. The fibular nerve wraps around the fibular neck, where a tight cast or prolonged leg crossing can cause foot drop.
| Nerve | Motor test | Sensory test |
|---|---|---|
| Femoral | Straighten the knee | Front of the thigh |
| Obturator | Squeeze the knees together | Inner thigh |
| Tibial | Push the foot down | Sole of the foot |
| Deep fibular | Lift the foot and big toe up | Web space between the first and second toes |
| Superficial fibular | Turn the foot outward | Top of the foot |
At the bedside
Check pulses, color, movement and sensation of the foot before and after splinting or casting a leg. Loss of protective sensation on the sole is a key finding in the diabetic foot exam because it raises the risk of unnoticed injury.
Related guides
Written by Making Synapses. Topic reference: OpenStax, Anatomy and Physiology 2e (no text adapted).