The reasons why the left rib cage is more convex than the right rib cage include rib cage inflammation, rib cage trauma, and developmental deformity of the rib cage. 1. Inflammation of ribs: common is costochondritis, due to the inflammation of the rib bone hyperplasia, there is a deformation of the ribs, etc., which may be manifested as the left rib is more convex than the right rib. 2. Rib trauma: due to the direct action of violence, resulting in rib fracture, poor fracture healing, the left side of the rib cage is more convex than the right side of the rib cage. 3. Developmental deformity of ribs: it is a developmental deformity. Other causes may also include rib tumors. When the left side of the rib cage is more bulging than the right side of the rib cage, you should go to the hospital at the first time, to clarify the cause of the disease, early diagnosis and early treatment.