The vast majority of cases of sitting leg swelling are caused by lower extremity venous valve insufficiency. In the case of lower extremity venous valve insufficiency, sitting for a long time will cause the loss of muscle pumping effect of the calf, so that the venous return of the lower extremity is obviously stagnant in the calf, resulting in swelling of the calf. If this happens, you should go to the vascular surgery department as soon as possible and have a color ultrasound examination of the veins of the lower limbs, which can clearly determine whether there is lower limb venous insufficiency or not. However, in the early stage of lower limb venous insufficiency, you need an experienced color ultrasound physician to diagnose it, and after the diagnosis is clearly defined, you can carry out a conservative or active treatment.