An obese patient is brought into the casualty in shock and in need of intravenous fluids. No superficial veins can be seen or palpated. The emergency room physician decides to make an incision to locate the great saphenous vein for the inseion of a cannula ("saphenous cutdown"). In which of the following locations should the incision be made?

The great saphenous vein is one of the two major superficial veins of the lower limb. It is found in the superficial fascia, where it is accessible for procedures such as saphenous cutdown and saphenous venous graft. As the vein ascends along the lower limb, it passes anterior to the medial malleolus at the ankle and posterior to the medial side of the knee. The vein then passes through the saphenous hiatus of the fascia lata to empty into the femoral vein slightly below the inguinal ligament.No major vein is found anterior to the lateral malleolus. Veins on the dorsum of the foot are small tributaries of the great and small saphenous veins. The small saphenous vein passes posterior to the lateral malleolus.