Diaphragmatic endometriosis is a lesser-known form of extra-pelvic endometriosis that can cause pain in the ribs, upper abdomen, chest, shoulder, or upper back — often around a person’s period or hormonal flares. Because these symptoms do not always sound “gynecological,” they can be confusing, dismissed, or mistaken for something else. This article explains what diaphragmatic endometriosis is, why shoulder and rib pain can happen, what symptoms to track, and when to seek med