Normally, the valves in your veins work in a “one way” direction as blood flows toward your heart. When these valves don’t work well, blood can also flow backward. This can cause blood to collect (pool) in your legs. If untreated, debilitating symptoms can occur such as pain, cramps, swelling, skin changes, varicose veins, and leg ulcers. Other common causes of venous disease include a history of Deep Vein Thrombosis (DVT) and obstruction in the Iliac veins.