There are more reasons for leg swelling, which may be related to lactic acid accumulation, renal insufficiency, and venous thrombosis of the lower limbs. 1. Lactic acid accumulation: it may be that the patient stands or walks for a long time, which leads to long time tightness of leg muscles. Or lactic acid produces too much and is not metabolized in time, which may affect blood circulation and show the phenomenon of leg swelling. 2. Renal insufficiency: In patients with renal insufficiency, the renal filtration rate is reduced, resulting in water and sodium retention in the body, which cannot be discharged from the body in time, and collects in the lowest part of the body, thus resulting in the symptom of swollen legs. 3. Lower extremity venous thrombosis: If the lower extremity veins have thrombosis, the venous return of the lower extremity is blocked, which may also lead to leg swelling, but this swelling is usually asymmetric swelling of both legs. Leg swelling can also be seen in pregnancy, sedentary standing and other factors, it is recommended to consult a doctor in a timely manner, follow the doctor’s instructions for further examination, with the help of the doctor to clarify the cause, and targeted treatment or therapy.