http://goldmanveininstitute.com/signs-symptoms/leg-pain-swelling/ description: Leg discomfort and swelling can be caused by a variety of conditions, including varicose veins. Venous blood is full of toxins, and the purpose of veins is to route that toxic blood up to the heart where it gets refreshed. This action is a combination of a pump (the calf) and small check valves that are strategically placed throughout the venous system, allowing venous blood to only pass in the upwards direction.