Left back subcostal bone pain may be due to muscle injury, kidney disease, costochondritis. 1. Muscle injury: If you are engaged in long-term sports or often work a lot, it may lead to long-term muscle or tendon strain, which may cause muscle injury and form aseptic inflammation, and the repeated stimulation of inflammation will cause the symptoms of left back subcostal bone pain. 2. Kidney disease: pain in the lower side of the left rib cage in the back of the human body may also be due to kidney disease, such as hydronephrosis, kidney stones, kidney tumors and other diseases, which will cause stimulation or compression of the local tissues, resulting in symptoms of pain. 3. Costochondritis: When costochondritis occurs in the left back of the rib cage, it will lead to pain here, which is mainly due to inflammation stimulation of peripheral nerve tissue resulting in pain. In addition, costochondroma, heart disease, lumbar spine disease can also cause pain in the left back of the subcostal bone, so it is recommended to go to the hospital in time for examination, a clear diagnosis and then follow the doctor’s instructions for targeted treatment, do not be negligent, to avoid aggravation of the condition.