(HealthDay News) -- A dangerous condition called deep vein thrombosis (DVT) occurs when a blood clot develops in a vein deep inside the body.

The U.S. National Heart Lung and Blood Institute mentions these potential risk factors:

  • Having had a previous DVT, or taking medication that thickens the blood or promotes clotting.
  • Having had surgery, a broken bone or other injury that affects a deep vein.
  • Having reduced blood flow to a deep vein as a result of inactivity. Typical causes are post-surgical recovery, or taking a long trip that limits your ability to move around.
  • Being pregnant.
  • Being treated for cancer.
  • Having a central venous catheter.
  • Being over the age of 60, being a smoker or being obese.