If the same posture is maintained for too long, it may lead to temporary left lower limb numbness, which can disappear after changing posture. If there is no obvious cause for left lower extremity numbness, it is mostly considered as lumbar spine disease, cerebrovascular disease, peripheral nerve disease, diabetes, lower extremity vascular disease, tumor, etc. 1, lumbar spine disease: common lumbar disc protrusion, the protruding nucleus pulposus of the lumbar spine will compress the nerve root on one side, resulting in numbness of one lower extremity, which can be accompanied by pain. At this time, CT and MRI can be done for early diagnosis and treatment; 2, cerebrovascular disease: patients with thalamic infarction may have symptoms of numbness on one side of the limb, usually patients are older and usually have chronic diseases such as hypertension and diabetes, and cerebral infarction lesions can be seen on cranial MRI. If the sensory conduction pathway is damaged, numbness of the left lower limb can be triggered, and it can be accompanied by other symptoms of neurological deficits, such as limb weakness and dizziness, etc.; 3. Peripheral nerve diseases: infection and post-infection metabolic and endocrine disorders, connective tissue diseases, genetics and other factors can trigger neurological diseases, which can manifest as limb numbness. Some diseases also compress the left lower limb nerve, causing left lower limb numbness, such as pear-shaped muscle syndrome, common posterior thigh, lateral numbness with pain; 4, diabetes: vasculopathy and peripheral neuropathy are two common complications of diabetes, high glucose state leads to lower limb microvascular damage, local ischemia, hypoxia, which leads to changes in peripheral nerve function, the symptoms of numbness in both legs. For this condition, blood sugar control and active treatment of the primary disease are required. In addition, nerve nutrition through oral methylcobalamin and vitamin B12 and warm water foot soaking can improve blood circulation in the legs; 5. Lower limb vascular lesions: they can be manifested as venous lesions, such as varicose veins, and arterial lesions, such as arterial embolism, which can lead to numbness in both feet and increased swelling when standing and walking, etc. Surgical treatment can be performed, such as high saphenous vein ligation and stripping, catheter blood extraction, etc.; 6, tumor: such as spinal cord tumor, bone tumor, compression of nerves, will lead to left lower limb numbness, need to promptly seek medical attention, after relevant examination, choose suitable treatment methods, surgery or radiotherapy, etc. Patients with symptoms of left lower extremity numbness need to go to the neurology department in time, the doctor will determine the specific cause through medical history, accompanying symptoms combined with auxiliary examinations, and after clarifying the cause, carry out the cause and symptomatic treatment.