Back pain during menstruation is a relatively common manifestation of menstrual syndrome, and there are several specific causes. First, when menstruation comes, the menstrual blood will reach the pelvis through the fallopian tube, and a large amount of menstrual blood will exist in the pelvis. The absorption of menstrual blood needs a process, and during the absorption period it will stimulate the pelvic blood vessels and even the blood vessels in the lumbar-sacral area, which will lead to the manifestation of soreness and pain in the lower abdomen. Second, when menstruation comes due to the persistent release of prostaglandins causing dysmenorrhea, so it will also stimulate the nerves of the sacral ligament and appear lumbar pain. Third, due to the arrival of menstruation in the pelvic blood vessels belong to the state of rapid expansion, will cause small abdominal and lumbar pain now, which is normal. It is normal and will subside after the end of menstruation and will not affect the health of the body.