There are many reasons for back pain before menstruation, such as normal phenomenon, endometriosis, pelvic inflammatory disease and so on can lead to. 1. Normal phenomenon: the estrogen and progesterone secreted by the body before menstruation will fluctuate greatly, and the back of the uterus will press the rectum and lumbosacral area, which is easy to appear the symptoms of lumbar pain. 2. Endometriosis: it means that the active endometrial cells are planted in a location other than the endometrium, and it is often characterized by dysmenorrhea, chronic pelvic pain, abnormal menstruation and infertility, etc. If the endometrium is ectopic to the lumbosacral region, it may manifest itself as the symptom of lumbar pain before menstruation. 3. Pelvic inflammatory disease: it refers to the inflammation of female reproductive organs, connective tissues around the uterus and pelvic peritoneum, which is mainly characterized by lower abdominal pain, fever, increased secretion, etc. Some patients have symptoms of lumbar pain before menstruation due to the stimulation of inflammation. In addition, lumbar muscle strain, lumbar spondylosis, lumbar intervertebral disc herniation, etc., can also lead to lumbar pain before menstruation. If the patient has a sore back before menstruation, he or she should consult a doctor in a timely manner to clarify the specific cause of the disease, and then follow the doctor’s instructions for treatment.