Diseases of the veins are varied. There can be problems with clotting in the veins, such as deep vein thrombosis, a serious medical condition. Another condition is venous reflux disease, a problem with the valves within the superficial veins. When working properly, the valves keep blood moving up the legs and towards the heart. When the valves are not functioning properly, blood will reflux back towards the feet causing swelling, aching, heaviness, itching and burning, and eventually can develop into varicose veins.