Connecting the low pressure superficial veins to the high pressure deep veins are a series of perforating veins whose valves are oriented to only permit flow from the superficial venous system to the deep venous system. When the perforator valves fail to close properly, the high pressure created by the musculovenous pump can force the blood in the deep venous system back out to the skin level. This can be identified as a “blown out vein” and causes a palpable defect in the covering of the muscle layer (fascial defect) to enlarge and feel like a hole in the muscle surface. There are several important Perforator Veins in the inner (medial side) of the ankle and calf called Posterior Tibial Perforators (Crockett’s perforators) which connect to the Posterior Arch Vein and the deep veins in the calf. At the top of the inner portion of the calf there are Paratibial Perforator veins (Boyd’s Perforator) . The Dodd’s perforators are located at the lower inner thigh level and the Hunter’s Perforators are located in the upper inner thigh level. Collectively the perforators in the thigh are called the Perforators of the Femoral Canal. Another important connection is the Posterior Thigh Extension Vein (Intersaphenous Vein or Vein of Giacomini) which runs from the Popliteal Vein behind the knee and joins the Great Saphenous Vein just below the SFJ. This intricate system of interconnections allows the venous return of the leg to seek alternative routes around a blood clot in the deep vein of the leg and return venous blood to the groin through the superficial venous system. Failure to detect malfunction of the perforator system (venous reflux from incompetent valves) by an inexperienced practitioner is one of the chief causes for failure and ultimate patient dissatisfaction after venous ablation procedures.