1. What is adenomyosis? (brief overview). Adenomyosis is a condition where tissue similar to the lining of the uterus (the endometrium) grows into the muscular wall of the uterus (the myometrium). This can make the uterus thicker, larger, and more prone to heavy bleeding, cramping, or chronic pelvic pain. It most commonly affects women in their 30s and 40s, but it can occur at other ages...