The common causes of leg pain after walking 500 meters three months after lumbar spine fracture surgery are decreased muscle strength, venous thrombosis, degenerative changes of knee joints, and so on. 1. Decrease in muscle strength: long time bed rest after fracture, lack of activity of the lower limbs, resulting in muscle atrophy of both lower limbs, muscle strength is not enough at the beginning of the resumption of walking, the accumulation of muscle lactic acid after the activity causes leg pain, which is a normal phenomenon. 2. Venous thrombosis: because the lumbar vertebral fracture needs to stay in bed for a long time, the activity of the lower limbs is obviously reduced, and the blood circulation will be slowed down, which will easily cause venous thrombosis in the lower limbs, and the thrombus occlusion can cause the lower limbs to be sore. 3. Knee degenerative changes: the elderly due to old age, long-term chronic strain and other reasons, resulting in degenerative changes in the knee joints, coupled with the lack of activities after the lumbar spine fracture, the lower limb muscle strength is weakened, the support ability to reduce the load on the knee joints, causing pain in the lower limbs. Causes of lumbar spine fracture surgery after three months of walking pain causes more, if the symptoms continue to not relieve, it is recommended to consult a doctor in a timely manner, to clarify the cause of the disease, targeted treatment.