Three factors are thought to contribute to the formation of blood clots (Virchow's Triad):
-blood vessel damage
-interrupted blood flow or turbulence
-congenital or medical problems that cause someone to be predisposed to clots
Some of the well-known risk factors that health care workers focus on are: sitting down or laying still for extended periods of time, blood clotting disorders, heart arrhythmias, and cancer.