Chronic venous insufficiency occurs when your leg veins do not allow blood to flow back up to your heart. Normally, the valves in your veins make sure that blood flows toward your heart. But when these valves do not work well, blood can also flow backward. This can cause blood to collect (pool) in your legs.
Chronic venous insufficiency can develop from common conditions such as varicose veins. It can also occur if something, such as deep vein thrombosis, damages the valves inside the veins.
Over time, as the veins become increasingly weak, they have more trouble sending blood to the heart. Tiny valves in the veins can fail. As a result, blood pools in the lower limbs causing pain, swelling, and other circulation problems.