Causes of pain in the side of the rib cage include chest wall skin diseases, trauma, and rib cage diseases. 1. Chest wall skin diseases: such as acute dermatitis of the side of the rib cage, herpes zoster, subcutaneous cellulitis and so on, all of which can cause pain in the side of the rib cage. 2. Trauma: rib fracture, dislocation of thoracic and rib joints, soft tissue contusion, etc. caused by car accident trauma, crush injury, etc., can also cause lateral rib pain, usually with a clear history of trauma. 3. Rib diseases: such as intercostal neuritis, costochondritis, and multiple myeloma, acute leukemia and other invasion of the ribs, can cause pain in the side of the ribs. There are many causes of lateral rib pain, patients should consult the doctor in time for early treatment, so as to avoid delaying the condition and affecting the prognosis.