Inside your veins, there are small valves that help support the weight of the blood in the veins and drive the venous blood flow back to the heart for re-circulation. When a blood clot (DVT) forms in the deep leg veins, the valves become damaged and no longer close properly, which leads to venous blood pooling and increased venous pressure.

The damaged or incompetent valves is known as chronic venous insufficiency (CVI). CVI represents a chronic mechanical problem that leads to reduced blood flow, swelling, and limb pain. This chronic condition is called post thrombotic syndrome. In addition to causing pain and swelling, post thrombotic syndrome increases the risk of additional blood clots.