The reasons for sudden inability to walk on the leg are as follows: 1. If it is one leg, consider it to be caused by cerebrovascular disease. It can be seen in cerebral hemorrhage or cerebral infarction in the radioactive coronary area that leads to monoplegia, and the diagnosis is confirmed by CT or MRI examination of the head. Treatment can be given to the patient for cerebral hemorrhage or cerebral infarction, and also to prevent recurrence of cerebrovascular disease.2. Sudden inability to walk can also be seen clinically in patients with lumbar spinal stenosis. The diagnosis can be confirmed by CT or MRI of the lumbar intervertebral disc. 3. Sudden inability to walk can also be seen in lower limb arteriosclerosis occlusive disease, where the patient has heavy arteriosclerosis. The patient’s arteriosclerosis is more severe. Due to the occlusion of the arteries in the lower extremities, there can be sudden inability to walk, and it can be accompanied by pain, so you can check the ultrasound of the arteries in the lower extremities. 4.