The pain in the buttocks and legs after walking may be caused by lactic acid accumulation, lumbar disc herniation, femoral head necrosis and other diseases. 1. Lactic acid buildup: If patients who have not exercised for a long time suddenly do a lot of exercise, it will easily lead to the accumulation of lactic acid in the buttocks and legs and other muscle-rich locations, which may cause soreness in the buttocks and legs. 2. Herniated lumbar intervertebral discs: If the patient experiences radiating pain and numbness in the buttocks and legs, which is aggravated when walking and alleviated when squatting or sitting, it is considered that it may be caused by the pressure on the sciatic nerve due to the herniated lumbar intervertebral discs, which is accompanied with lumbago and intermittent claudication in some of the patients. 3. Necrosis of the femoral head: Necrosis of the femoral head is caused by ischemia of the femoral head due to trauma, long-term use of hormonal drugs, ethanol poisoning and other factors, usually asymptomatic or only mild discomfort in the hip, with the development of the disease, the patient may have acute hip pain, radiating pain in the buttocks and legs, and joint activities are obviously limited. In addition, sciatic neuritis, sacroiliac arthritis, lumbar spinal stenosis, pyriformis syndrome and other diseases may also cause pain in the buttocks and legs after walking, and it is recommended that the patient consult a doctor for examination in time to clarify the cause of the disease and then carry out targeted treatment.