The most common causes of swollen legs after walking are lower extremity varicose veins, lower extremity venous thrombosis and heart failure. Mainly: 1, varicose veins of the lower extremity patients most often appear leg swelling, because when there are varicose veins of the lower extremity will lead to lower extremity venous reflux obstruction, long time standing or walking due to gravity, coupled with the existence of varicose veins of the lower extremity, lower extremity venous blood flow to the heart will be obstructed, which will lead to increased pressure in the veins of the lower extremity cause leg swelling; 2, lower extremity venous thrombosis is also a common cause of leg swelling. The presence of thrombosis in the veins of the lower limbs will cause the inflow of blood into the veins of the lower limbs to be affected by the heart, which will lead to an increase in the pressure in the veins of the lower limbs, and the blood will leak through the walls of the blood vessels into the tissue interstices and cause leg swelling; 3. Patients with heart failure are also prone to leg swelling, such as renal insufficiency and hypoproteinemia, which also easily cause swelling of the lower limbs.