Varicose veins are most often swollen, gnarled veins that most frequently occur in the legs, ankles and feet. They are produced by a condition known as venous insufficiency or venous reflux, in which blood circulating through the lower limbs does not properly return to the heart but instead pools up in the distended veins. They may cause pain, swelling and even skin ulcerations. Most insurance plans will cover varicose vein treatment when symptomatic.