Anatomy of the superficial vessels and nerves of the gluteal region (buttocks) and thigh (left) and of the leg (right). In the leg the small saphenous vein (blue) passes behind the lateral malleolus at the ankle. Behind the knee it becomes deep to enter the popliteal vein which drains into the femoral vein. The sural nerve (yellow) accompanies the saphenous vein in the leg. From Sobotta, J. (1906) Atlas der deskriptiven Anatomie des Menschen. Vol 3, Das Nerven- und Gefasssystem des Menschen. J. F. Lehmann, Munchen, Figs. 530, 531.