In the middle of the front chest, on both sides of the sternum is where the ribs and rib cartilage are located. The following reasons may exist if the ribs or cartilage on both sides are not the same height: 1. Genetic factors are a common cause of this condition, some people are born with different heights of the ribs on both sides, but the difference in height is not obvious and is usually difficult to detect without careful examination and usually without any other discomfort or special performance. 2, This symptom may also occur if you often do heavy physical exercise or training, especially if you are used to using one limb for exercise. In the process of sports inevitably cause slight damage to one limb, easily causing the symptoms of one side of the ribs, rib cartilage protrusion, this will not have other uncomfortable symptoms. 3, there are also some adolescents with scoliosis, there must be different heights of performance on both sides of the thorax, because of the pulling effect of the scoliosis spine, making both sides different heights. The appearance of such symptoms, it is best to timely radiological examination to prevent aggravation of symptoms.