Endometriosis, polycystic ovary syndrome, fibroids: there are a ton of well-known conditions that can cause women and others excruciating pain. One condition of the reproductive system that you dont hear too much about is adenomyosis or endometriosis of the uterus muscle, as Dr. Natalya Danilyants of the Center for Innovative GYN Care likes to call it.

But you should hear about it, mostly because its fairly common. Its estimated that 1 in 10 women live with adenomyosis although those numbers could be off because there isnt a real standardized definition or diagnostic criteria for the condition.

Like endometriosis , in which uterine tissue lining grows outside the uterus, adenomyosis occurs when uterine tissue goes a bit awry. Tissue that should be lining the uterus instead builds up within the uterine muscle wall. Its a benign condition, meaning its not going to turn into cancer, but it can be very painful and even debilitating.