Hidden pain in the back of the left posterior rib cage may be caused by muscle strain, costochondritis, intercostal neuralgia and other reasons. 1. Muscle strain: usually due to overwork resulting in damage to the soft tissues of the muscles, the patient in the onset of pain, the back of the rib cage will appear hidden pain phenomenon. 2. Costochondritis: usually caused by viral infection or trauma to the costal cartilage, etc. When inflammation occurs, pain in the ribs may occur and spread to the back. 3. Intercostal neuralgia: usually due to rib fracture, thoracic disc herniation and other reasons, resulting in damage to the intercostal plexus, the symptoms of left posterior rib back pain may occur. Left back rib back pain may also be other reasons, such as trauma, heart disease, lung tumor, etc., please consult the hospital in time, and actively diagnosis and treatment, so as not to delay the condition.