The painful sensation in the buttocks during menstruation is mainly caused by a retroflexed and retroverted uterus that irritates the rectum. If there is abdominal massage during menstruation, it may lead to reflux of menstrual blood, which means that menstrual blood enters the pelvic cavity along the fallopian tube and reaches the rectal fossa of the uterus, causing a painful sensation in the buttocks. Also, due to endometriosis, the cramping sensation is caused by the foci of endometriosis during menstruation. In addition, chronic pelvic inflammatory disease can also cause a painful sensation in the buttocks during menstruation. Therefore, it is recommended to have a gynecological examination after menstruation, mainly to exclude endometriosis and pelvic inflammatory disease, and to find out whether the position of the uterus is retroflexion and retroversion.