Deep vein thrombosis (DVT) occurs when a blood clot forms within a deep vein, most often in the calf or thigh area.
The American Academy of Orthopaedic Surgeons offers this list of risk factors that may increase the likelihood of DVT:
Having had a pulmonary embolism or a previous case of deep vein thrombosis.
Having had cancer that has spread.
Having had another vein condition, such as varicose veins.
Being a smoker.
Taking estrogen.
Being pregnant.
Being obese.