When patients find a protrusion on the lower left side of the rib cage, they should go to the hospital in time for examination, preferably in some large hospitals, and can take X-rays or MRI to clarify the situation of the rib cage protrusion. Usually, the protrusion of the lower left rib cage is caused by a variety of reasons, as follows: 1. When a patient has costochondritis, the lower left rib cage will protrude, and painful sensations will occur, and the patient can take anti-inflammatory and pain-relieving drugs for treatment. 2. 3. The rib protrusion may also be caused by a bone tumor, which needs to be treated according to the specific cause. In short, when patients find that their ribs are protruding, they should go to the hospital for examination as soon as possible.