Dysmenorrhea is the medical term for painful periods — cramping pain in the lower abdomen, sometimes spreading to the back or thighs, around the time of menstruation. It's caused largely by prostaglandins, which make the uterus contract.
Doctors distinguish primary dysmenorrhea (common period pain with no underlying disease) from secondary dysmenorrhea (pain from a condition such as endometriosis, fibroids or adenomyosis). Heat, NSAIDs used as directed, gentle movement and, for some, hormonal options can help. Pain that is severe, worsening, or disrupts your life should be assessed. See period pain.