Stiffness of the lower leg, thickening and swelling of the lower leg after prolonged sitting and standing is caused by prolonged sitting and standing, which leads to compression of the blood vessels in the lower limb, thus causing poor vascular reflux in the lower limb, which can cause stiffness of the lower leg and swelling of the lower limb after prolonged sitting and standing. Especially patients who suffer from varicose veins in lower limbs are more likely to have this situation. In addition, patients with lower limb vein thrombosis can also have lower limb swelling. Lower limb vein thrombosis is a more dangerous disease because once the lower limb vein thrombosis is dislodged, it may enter the pulmonary artery with the vein and cause pulmonary embolism. It may endanger the health of the patient, and even the life of the patient in serious cases, so in this case, you need to go to the hospital to check the lower limb vascular ultrasound for a clear diagnosis, and according to the cause of the disease for targeted treatment.