Lower extremity atherosclerosis can be divided into four clinical periods according to the course of the disease: 1, the mild symptomatic period: early onset, most patients are asymptomatic or have only mild symptoms, such as coldness of the affected limbs, fear of cold, walking easily fatigue, etc. 2, intermittent claudication period: is the characteristic performance of atherosclerotic occlusive disease. With the development of lesions, the degree of arterial stenosis and the scope of obstruction of the lower limbs are increasing, and the diseased arteries can only meet the blood supply of the muscle tissue of the lower limbs in the resting state. When the lower extremity walking movement, the lesion artery can not meet the muscle tissue more blood perfusion requirements, the acidic metabolites of the muscle to produce soreness in the lower leg, the patient is forced to stop for a period of time to rest before continuing to walk. The progression of the lesion results in shorter and shorter intercambular distances and longer and longer rest periods. The location of the pain can be the calf or the thigh part. 3, resting pain period: when the lesion artery can not meet the resting state of the lower limb blood supply, the patient is produced resting pain. The pain site is usually in the front half of the affected limb or toe end, and it is easy to occur at night and when lying down. Patients prefer to bend their knees and often sit with their knees in their arms throughout the night. Some patients are unable to straighten their joints due to the stiffness of the knee joint caused by prolonged knee bending. Resting pain is a precursor to gangrene of the affected limb and should be treated as soon as possible. 4. Ulcerative and necrotic phase: When the skin blood perfusion of the affected limb cannot meet even the most basic metabolism, the slightly damaged tissue cannot be repaired and the area of necrosis keeps increasing, which eventually leads to gangrene and necrosis of the limb.