Lateral thigh pain may be caused by physiological factors such as strenuous exercise and long time running, or it may be caused by pathological factors such as muscle strain, lumbar spinal stenosis and pyriformis syndrome. 1. Physiological factors: if strenuous exercise or running for a long time, can cause thigh muscle strain, the body produces excessive metabolic products, lactic acid accumulation, resulting in pain in the outer thighs, without special treatment, can be gradually relieved after sufficient rest. 2. Muscle strain: trauma or strenuous exercise can cause muscle strain, which will cause pain in the outer thigh, usually accompanied by localized swelling, acute injury requires timely ice. 3. Lumbar spinal stenosis: due to congenital malformation of the lumbar spine, degenerative changes in the lumbar spine or lumbar spine trauma and thus cause lumbar spinal stenosis, compression to the spinal nerves traveling in it, can cause numbness and pain in the lateral thigh. 4. Piriformis syndrome: when the piriformis muscle is damaged for various reasons, it is easy to form edema and congestion in the local area, which in turn causes compression of the sciatic nerve and pain in the lateral thigh. Causes of lateral leg pain are more reasons, may also be associated with skin infections, tumors and other causes, if the symptoms continue to be unrelieved, it is recommended to promptly go to the hospital to identify the cause of the disease, and then targeted treatment.