Correct answer:

Besides the saphenofemoral and saphenopopliteal junctions, there are additional communications between superficial and deep veins with valves allowing blood in the superficial system to pass into the deep system, and preventing blood flowing out from the deep to superficial veins. These are called perforating veins, or perforators. Typically there is one mid-thigh (called the hunterian perforator on account of its relationship to Hunter’s canal), and several running up the medial and lateral aspect of the tibia just above the ankle.