Left-sided back pain may be caused by exertion, trauma, localized fasciitis, spinal disorders and other diseases. 1. Physiological factors: due to excessive stooping for labor, resulting in the accumulation of metabolic products in the muscles of the low back, left-sided back pain can occur, which can be relieved after rest. 2. Trauma: due to trauma and other factors acting on the left side of the back, resulting in back bone, muscle and other tissues of the injury, left side of the back pain can occur. 3. Localized fasciitis: aseptic inflammation of localized fascia caused by long-term labor, cold and other factors can cause left-sided back pain. 4. Spinal diseases: including intervertebral disc herniation, vertebral tumors and other diseases, compression or irritation of paravertebral nerves, can cause left-sided back pain. 5. Other diseases: heart disease, acute pancreatitis, spleen disease and left kidney disease can cause left back pain. As the causes of left back pain are many, it is recommended to go to the hospital in time to improve the examination and further treatment after clarifying the cause.