The common causes of restless legs syndrome, lower extremity venous valve insufficiency, muscle strain, and so on. 1. Restless legs syndrome: it may be related to heredity, disease and psychological factors, which makes it difficult to sleep at night and always want to straighten the legs. 2. Venous Valve Insufficiency of Lower Extremity: due to long time standing or walking during the day, the blood circulation in the veins of the lower extremity is not smooth, and the venous return circulation is impaired and appears. 3. Muscle strain: lower limbs such as cold and overwork, etc., may cause muscle strain of the lower limbs, aseptic inflammation, inflammation stimulation will appear above symptoms. Caused by the night sleep legs always want to straighten, there may be other reasons, it is recommended to go to the hospital in a timely manner, improve the examination to clarify the cause of the disease, under the guidance of the doctor for standardized treatment.