Your body reacts to the injury of surgery no differently than to an accidental injury. To limit blood loss, it raises coagulation factors in the blood. Unfortunately, this increases the risk of developing blood clots after surgery, which is further amplified by long periods of inactivity during bed rest and the direct impact on blood vessels caused by the surgical procedure.
DVT (deep vein thrombosis) most commonly occurs if a blood clot in the leg forms in the deep veins of the calf muscles. Less often, it may form in the deep veins of the thigh. It can also sometimes affect arms or block other deep veins within the body. If a part or all of the clot breaks free and travels in the bloodstream to obstruct arteries in the lungs, this can cause a potentially fatal pulmonary embolism (PE). DVT and PE are often referred to collectively as venous thromboembolism (VTE).