Left-sided back pain can be seen in back muscle strain, myofasciitis, cervical spondylosis, coronary heart disease, angina pectoris, thoracic disorders and other diseases, as follows: 1, strain, cold: strain, cold and other reasons, causing aseptic inflammatory reactions in the back muscles, fascia and other tissues, can cause local pain, mostly in forward bending and backward when the pain increases, the pain often disappears when resting in bed. 2, cervical spondylosis: cervical spondylosis 3, heart disease: coronary heart disease, angina pectoris, and even myocardial infarction can also cause pain in the back, and sometimes the pain may also radiate to the left side of the inner upper arm, accompanied by pain in the precordial region, chest tightness, pressure-like tightness and other manifestations. 3, other diseases: inflammation of the thoracic organs, tumors and other disorders may also cause pain in the back, sometimes accompanied by cough, fever and other symptoms. If the pain is not relieved after resting, it is necessary to pay great attention to the left side of the back pain and go to the hospital for a clear diagnosis to exclude cardiopulmonary disorders. If the pain is caused by muscle and fascia strain, inflammation is mostly relieved after rest and often relieved more rapidly after taking NSAIDs and analgesics, which usually do not cause serious problems.