Lying down, the left rib cage is higher than the right rib cage may be caused by normal phenomenon, trauma, rib cartilage deformity, osteoporosis and other reasons. 1. Normal phenomenon: when the stomach of human body gets full and lasts for a long time, it can affect the development of the rib cage, and the left rib cage is higher than the right rib cage. 2. Trauma: When the body suffers from trauma, it may trigger the left side of the ribs into multiple fractures, through the treatment of the fracture, the ribs may be deformed healing, which will appear to lie down the left ribs are higher than the right ribs. 3. Rib cartilage deformity: malnutrition, osteoporosis, heredity and so on may induce rib cartilage deformity, and there may be the case that the left rib is higher than the right rib when lying down. 4. Osteoporosis: most of the osteoporosis is caused by lack of calcium. Osteoporosis occurs when the bone grows, which will cause bone dysplasia, and the left rib is higher than the right rib when lying down. It is recommended to go to the hospital for examination, and the doctor will give the appropriate treatment according to the specific situation.