Most cases of thick legs and thin legs are due to venous insufficiency in the lower limbs. When valve insufficiency occurs in the veins of the lower extremities of the body, it is equivalent to a valve in the blood vessel that is not closed properly. This valve is one-way open, if the valve is broken, it will lead to a part of the blood from the heart backflow back into the blood vessels, causing the thickening of the blood vessels, pressure increase, the contents of the vessels seepage, resulting in edema between the tissues, causing thick legs, this situation often occurs after a long time standing, sitting, after standing up activities or affected limbs elevated, because of the promotion of the lower limb venous reflux, so the situation will be significantly reduced, so there will be legs The situation of thick and thin at one time.