The common causes of pain in the left rib cage are costochondritis, left rib fracture, and intercostal nerve inflammation, as follows:1. Costochondritis: viral infection or local trauma can cause costochondritis, and the patient will have localized pain and swelling, accompanied by limited breathing activities.2. Left rib fracture: intense trauma may cause rib fracture, and the patient may have pain in the left thoracic rib cage, dyspnea, etc. X-ray film can confirm the fracture line, and early immobilization can provide complete relief of the symptoms.3. X-ray can diagnose the fracture line, and early fixation can relieve the symptoms completely.3. Inflammation of intercostal nerves: Trauma or infection can cause inflammation of intercostal nerves, which can lead to pain in the periphery of the left ribs, and the pain can be widely spread to the intercostal space, which can cause pain in the whole chest and ribs. Through active treatment can make the left rib pain symptoms have been significantly relieved, but first of all should be clear cause, so as to choose the correct treatment.