Blood Clot formation (thrombus) inside the blood vessel is called thrombosis. The tendency of blood clotting takes place when the person is having vein injury or having blood tendency towards clotting or even when people are immobile. There will be an obstruction for the flow of the blood because of blood clot through the circulatory system. When there is an injury to the blood vessel the body utilizes platelets and fibrin for the formation of blood clot, the primary step in repairing it is to prevent loss of blood (hemostasis). If this mechanism causes too much clotting the clots breaks leading to formation of an embolus. Partially thrombosis can be prevented by anticoagulant. Deep vein thrombosis is one of the most common types of venous thrombosis