How does thrombophlebitis occur?

Three main reasons. Thrombophlebitis is venous thrombosis and associated inflammation of the affected vein. Also referred to as DVT or deep vein thrombosis. It is almost always the result of one or more of 3 conditions (known as virchow's triad): 1stasis of blood, 2 endothelial injury or 3 hyper-coagulability. Common causes for each: 1 long trip 2 post surgery or trauma 3 birth control pills or blood disorder.