Pain in the legs below the knee may be caused by the following reasons: 1. local stimulation by wind and cold or prolonged cold air conditioning or fan blowing on the joints of the legs, resulting in stimulation by wind and cold and inducing pain. 2. lumbar disc protrusion, lumbar spinal stenosis, lumbar spondylolisthesis, etc., compressing the nerves of the lower limbs and inducing pain. 3. venous thrombosis or atherosclerosis formation or stenosis of the lower limbs, etc. The pain is induced by the obstruction of reflux or insufficient blood supply, and should be seen by the hospital in time.