Chronic venous insufficiency (CVI) occurs when your leg veins cannot pump enough blood back to your heart due to damage to the vein valves.
Vein valves are one-way flaps that help blood in your legs to flow against gravity when a person is in the upright position. Sitting or standing stationary for long periods of time may cause the veins to stretch, which can weaken the vein walls and damage vein valves.
When these valves are damaged, the blood leaks and pools in the legs and feet. CVI is a long-term condition and occurs because of partial vein blockage or blood leakage around the valves of the veins.