Adenomyosis occurs when endometrial tissue grows into the muscular wall of the uterus. There are two types: diffuse, where tissue is scattered throughout the wall, and focal, where it grows in specific locations. Symptoms include pelvic pain, enlarged uterus, abnormal bleeding, and painful periods. Ultrasound can detect an enlarged uterus without masses and small cysts in the wall. Treatment options include hormone therapy, while hysterectomy provides the most effective treatment by removing the affected uterus.