If the legs swell up for no reason, it may be related to the following reasons: 1, there may be long-term standing, for example, some patients need to stand for a long time due to professional reasons, which will lead to poor blood circulation and poor reflux in the lower extremities, and the lower extremities may swell up, most serious after work, and lighter in the morning. 2, there may be vascular lesions in the lower extremities, for example, there is deep vein This is due to the increased viscosity of the blood and slowed blood flow, and the infrequent activities of such patients, such as frequent bed rest, may produce thrombosis in the large veins, which may lead to poor blood circulation and swelling of the lower limbs. 4. It may be caused by diseases related to internal organs, such as heart and kidney related diseases.