The most common cause of left-sided rib pain is a soft tissue contusion of the chest wall in the left quarter rib area. The most common cause is external impact on the left chest wall, or chronic strain on the left chest wall, often due to improper sleeping posture, and prolonged pressure on the left chest wall in the side-lying position can cause chest wall contusions, manifesting as pain in the left rib area. The first treatment is to correct the sleeping posture and avoid long hours of ambulation or twisting and reading, which can aggravate the intercostal muscle strain. Secondly, conventional non-steroidal anti-inflammatory drugs and muscle relaxants can be used to relieve pain and release muscle spasm.