Endometriosis causes pain during menstruation, mainly because the endometrium is shed at the same time as menstruation, which also causes localized bleeding from the ectopic lesion and therefore causes pain in the lower abdomen during menstruation and gradually increases, which is the characteristic of endometriosis causing dysmenorrhea during menstruation. After menstruation, pain in the lower abdomen is also caused, but the pain is reduced. The main reason why pain occurs after menstruation is that long-term endometriosis can lead to adhesions, which can reduce the elasticity of the local area, so pain can occur after menstruation. If there are endometriosis lesions that cause chocolate cysts in the ovaries, it is recommended to actively treat them with surgery.