Inner lining of all veins including the major deep veins have smooth surface, and a valvular mechanism to help venous (blue) blood that returns to the lungs for re-oxygenation to travel unhampered. With ageing plaques are formed in arteries, which obstructs the flow of oxygenated blood as in coronary artery disease. Such plaques never occur in veins under normal situation. Formation of clots in normal deep veins is called ‘Phlebo-thrombosis’ as opposed to clot formation in inflamed veins, called ‘Thrombo-plebitis’. Here being discussed on Phlebo-thrombosis or commonly called ‘Deep Vein Thrombosis’ (DVT).