Left paracostal pain, commonly seen in the following diseases: 1, consider the intercostal muscles strain, mostly due to long hours of work, sitting posture is not correct, such as often twisting the waist to read, play the computer, very easy to cause bilateral intercostal muscles force imbalance, will cause one side of the intercostal muscles strain, often manifested as the left side or the right side of the rib cage area pain, paracostal pain. 2, consider the chondritis of the rib cage, chondritis of the rib cage often The cause of chondromalacia is unknown, research shows that it may be related to mental stress and viral infection, and it mainly manifests as single rib pain and pressure pain.3. Considering intercostal neuritis, intercostal neuritis is mainly caused by viral infection, and the pain is mainly distributed along the intercostal space in the form of semi-circumferential distribution, and the pain is more intense, and it can present burning pain.