There are two types of veins, one causes spider veins these are little, the other causes varicous
veins and these are the big
veins, often the causes of lower leg ache, swelling
and colour change. You get relief from walking around, which suggests that being verticle restores the venous flow to the limb, aching and tight calf due to the blood flowing again. I just happened to be reading a very good article last night, i'll go find it for you.