What is lower extremity DVT? Veins are blood tubes that return blood to the heart. There are three types of veins: superficial veins are located under the skin, deep veins are located between the muscle groups, and transportation veins connect the deep veins to the superficial veins. The deep veins of the lower extremities lead to the largest vein in the body, the inferior vena cava, which flows directly back to the heart. Lower extremity DVT is a clotting of blood in the deep veins of the lower extremities that causes their lumen to become blocked. Lower extremity DVT tends to be acute in onset and can have serious consequences, such as dislodged blood clots that can cause acute pulmonary embolism, which can be life-threatening. Lower extremity DVT is so closely related to pulmonary embolism that the two conditions are clinically grouped together and referred to as thromboembolic disease. Most of the lower extremity DVT is acute in onset, the typical symptom is sudden swelling of the lower extremity, the lower extremity will be significantly thicker than the healthy side, the calf muscle will have obvious pressure pain, muscle tension will be high, and the serious can not walk on the ground. The skin color of the lower limbs will be purple, dark red, etc. What causes DVT? Venous thrombosis is caused by three factors: stagnant blood flow, damage to the vein wall and hypercoagulability, of which “stagnant blood” plays a big role. Stagnant blood flow occurs when a person is inactive for a long time. For example, prolonged bed rest, sitting for a long time without activity, are prone to slow blood flow, coupled with less drinking water, blood viscosity, etc. are prone to venous thrombosis. In addition, some major surgeries or after trauma, not only easily lead to blood vessel damage, but also increase the blood viscosity, are all risk factors for venous thrombosis.