Hidden pain inside the left rib cage may be caused by angina pectoris, pneumonia, pancreatitis and other diseases. 1. Angina: a heart disease caused by myocardial ischemia and ischemia, often sudden onset of pain in the precordial area, that is, the location of the second to fifth intercostal space in the left upper chest, and there will be dizziness, dyspnea, panic and other manifestations. 2. Pneumonia: It is an inflammation of the lungs caused by viruses or bacteria, and can also develop from respiratory infections, with clinical manifestations such as pain in the left internal rib cage, cough and shortness of breath. 3. Pancreatitis: Inflammation of the pancreatic tissue caused by prolonged excessive drinking, bile duct stones, overeating and other factors. The first symptom is pain in the left upper abdomen, i.e. the left 7-9 intercostal space, which is accompanied by nausea and vomiting. There may be other causes of left intercostal pain, so it is recommended to go to the hospital in time for relevant examinations.