What are the possible causes of left side muscle pain under the ribs?

This type of pain might have several causes. One possibility is twelfth rib syndrome, where the last rib becomes irritated and hurts the muscles nearby. Another possibility is intercostal neuralgia. This is when the nerves between your ribs, called intercostal nerves, become irritated or inflamed, causing pain. Painful rib syndrome is another condition, where the area around the rib, including soft tissues and muscles, becomes sore, often because of small injuries or strain. In addition, costochondritis, which is inflammation of the cartilage connecting your ribs to your breastbone, can cause pain under your ribs on one side. Sometimes, the pain might also be due to muscle strain from heavy lifting, awkward movements, or even poor posture. If you continue to have pain, you can use our free symptom checker to help identify possible causes, and it's important to talk to your doctor so they can determine the cause and help you feel better.