Thigh muscle pain after running may be caused by physiological reasons such as excessive exercise, pathological reasons such as fasciitis or osteoporosis in the thigh area. 1. Physiological reasons: it may be due to the amount of exercise, the accumulation of lactic acid within the muscle, resulting in pain and swelling, generally after rest can be relieved. 2. Pathological reasons: if you suffer from thigh fasciitis, local bursitis, the lesions will be repeatedly stimulated by external forces during running, which will cause pain in the thigh area. At this time to reduce running activities. Many elderly people, after the appearance of osteoporosis, there will be a lack of calcium, such as running again, may induce muscle pain. Thigh muscle pain after running may also be seen in other diseases, such as lumbar disc herniation, trauma, etc., if rest does not relieve, it is recommended to go to the hospital, improve the examination, clarify the cause of the disease under the guidance of the doctor, so as not to delay the condition.