Venous disease, or insufficiency, is when the valves stop doing their job as described above. Varicose veins are normal veins that have become abnormally enlarged because the blood, which no longer is flowing where it should, instead begins to pool in the vein. And while any vein may become varicose, the most common occurrences of varicose veins are in the legs and feet due to the extra strain that can happen from walking and standing.