Dr. Ruben’s Venous Insufficiency Article explains this condition thoroughly in his Woundsource article here.
Chronic venous insufficiency (CVI) refers to a long-term condition where the veins inside the legs have lost their ability to move blood back up to the heart from the legs. This occurs because the vein walls have weakened to the point where the venous pumps are no longer sufficient enough to send blood back up, against gravity, to the heart. CVI also affects the tiny valves inside the leg veins. When these valves do not close sufficiently, blood seeps back down past the valves and pools in the lower legs.