Saphenous nerve

At a glance

English

Saphenous nerve

Latin (TA2)

Nervus saphenus

System

Nerve

Region

Lower limb

Side

Paired, left and right

About the saphenous nerve

The saphenous nerve is the femoral nerve's end branch and its biggest cutaneous one. It arises from the posterior division of the femoral nerve in the femoral triangle, a little below the inguinal ligament.

From its origin it joins the femoral artery and runs with it down the femoral triangle into the adductor canal. In the canal it crosses from the lateral to the front of the artery. Near the lower end of the canal, where the femoral vessels pass through the adductor hiatus into the popliteal fossa, the nerve parts from them and leaves the canal through its roof. It then descends behind sartorius along the inner side of the knee and passes through the fascia lata between the sartorius and gracilis tendons, becoming subcutaneous a few finger-breadths above the medial femoral epicondyle.

Along the way it sends a twig to the subsartorial plexus in mid-thigh, which it shares with the obturator nerve and the anterior cutaneous branches of the femoral nerve. At the knee its infrapatellar branch pierces sartorius and the fascia lata to supply the skin over and below the kneecap and joins the peripatellar plexus. Below the knee it runs with the great saphenous vein along the tibia's medial border, giving medial crural cutaneous branches to the front and inner side of the leg. In the lower leg it divides: one branch follows the tibial margin to the ankle, and the other crosses in front of the medial malleolus to the inner border of the foot, often reaching the base of the great toe and linking with the superficial fibular nerve.

Its close company with the great saphenous vein puts it at risk when the vein is cut down on at the ankle, stripped for varicose veins or harvested for heart bypass grafts, and during incisions over the lower tibia or the medial malleolus. The infrapatellar branch is easily cut by knee arthroscopy portals or knee replacement incisions, leaving a numb patch beside the kneecap. Entrapment where the nerve leaves the adductor canal causes burning pain along the inner knee and leg, often at night or on stairs, with no weakness. The adductor canal block, which targets this nerve, gives pain relief after knee surgery while sparing quadriceps strength.

Course and supply

Arises from

The posterior division of the femoral nerve in the femoral triangle (L3-L4).

Ends in

Ends as cutaneous branches along the medial leg, the medial ankle and the medial border of the foot, sometimes as far as the base of the great toe.

Supplies

Purely sensory to the skin over the front of the knee, the medial and anteromedial leg, the medial ankle and the inner border of the foot.