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 clot (DVT) forms in the vein, the valves inside the vein can become damaged and no longer open and close. The damaged valves as well as residual clot create an obstacle for blood returning from the leg veins back to the heart, resulting in venous blood pooling and increased venous pressure.

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