The left intercostal bone hurts inside, and this condition is generally considered for the following three reasons: 1, intercostal muscle strain: the most common is intercostal muscle strain, mostly due to prolonged ambulatory work, and improper sitting posture, such as twisting the waist to sit, can cause bilateral intercostal muscle force imbalance, often manifesting as intercostal muscle strain on one side, reflecting the soreness and painful feeling in the rib area on one side. 2, intercostal chondritis: intercostal chondritis The cause is unknown, but current research suggests that it may be related to viral infection or mental stress stimulation, often manifesting as pain in a single rib. 3, intercostal neuritis: intercostal neuritis is mainly caused by viral infection. The pain is characterized by a semi-circular, band-like distribution of pain along one or both intercostal spaces, which is burning and pinprick-like.