PERFORATING VEINS:- Connect superficial with the deep veins. Small saphenous vein -1 perforator. Great saphenous vein perforators:- 3 medial perforators-just above ankle.1 perforator just below knee 1 in the region of adductor canal. These contain valves to prevent backflow of venous blood .i.e prevent flow from deep to superficial. Incompetence of these valves makes vein dilated and touous leading to varicose veins. If the valves in the perforating veins or at the termination of superficial veins become incompetent, the defective veins become "high-pressure leaks" through which high pressure of deep veins produced by muscular contractions is transmitted to superficial veins. This results in dilatation of superficial veins and to gradual degeneration of their walls producing varicose veins and varicose ulcers {Reference: BDC 9 E}