Hidden pain inside the left rib cage should be alert to left pleurisy, left costochondritis, myocarditis and other diseases. 1. Left pleurisy: it can be caused by bacterial, viral and other infections, and is an inflammatory reaction. At the beginning of the disease, there will be hidden pain in the chest, chest tightness, fever, muscle pain and other symptoms. As the disease progresses, the chest pain will be aggravated by deep breathing and coughing. In the late stage, the inflammation exudes a large amount of fluid, and the chest pain will be reduced. 2. Left costochondritis: It can be caused by strain, joint inflammation or bacterial or viral infection, etc. Rib pain is generally tolerable and may worsen when moving the body, breathing deeply or coughing. The pain may be aggravated when moving the body, taking a deep breath or coughing. The pain will be aggravated after exertion and alleviated after rest. 3. Myocarditis: most of the symptoms of viral infection before the onset of the disease, such as fever, generalized fatigue, muscle pain, some people will have hidden pain in the chest, and in severe cases, chest tightness and dyspnea will occur. Hidden pain inside the left rib cage may also have other causes, if the above symptoms occur, it is recommended to go to the hospital in time, after clarifying the cause of the disease, regular treatment.