If the left shoulder or back is sore, the following possibilities should be considered: 1) damage to the muscles or ligaments of the back, or the presence of frozen shoulder; 2) cervical spine diseases that cause soreness in the shoulder and back; 3) spinal and rib diseases that can also cause soreness in the left shoulder and back. You need to go to the orthopedic department of a hospital and have an X-ray or CT or MRI done to clarify the diagnosis. 4. The symptoms of soreness in the left shoulder and back cannot completely exclude heart disease, because when angina occurs, there will be some diffuse pain, and this diffuse pain can also lead to some diffuse pain in the left arm or shoulder and neck. In this case, the patient should have an electrocardiogram to see if there is a dynamic evolution of the electrocardiogram, or a coronary CTA or coronary angiogram to clarify the diagnosis.