There are three main reasons why the calf is always edematous. 1, due to vascular problems, such as local injury, strain, after the gradual formation of inflammatory lesions, will lead to local microcirculation is affected, there is a decrease in the function of small-vessel venous return, the local formation of inflammatory metabolites gradually increased, gradually formed inflammatory edema, easy to lead to the slowing of venous return, the formation of edema. It may also be due to thrombosis in the deep veins, resulting in slowed venous return and more and more venous blood in the distal end, which can lead to edema. The edema may also occur due to the excessive squeezing force between the legs and the chair due to prolonged sitting, resulting in the slowing down of venous return. 2. heart failure, after the heart failure, the venous return is severely restricted, which will easily make the lower extremities, especially the lower calves, appear obvious edema. 3. endocrine diseases, such as hyperthyroidism and immune system problems, will easily lead to edema. The problem of the immune system can easily lead to mucinous edema in front of the tibia, and this edema also usually occurs on both sides at the same time.