The pain on the left side of the back is mainly due to the following reasons: 1, lumbar muscle strain, such as prolonged sitting, squatting, standing and continuous bending, will lead to excessive muscle fatigue, gradually forming strain, will appear inflammatory lesions, the peripheral nerves around the stimulation will appear pain. 2, lumbar muscle and soft tissue strain, such as forceful bending, lifting heavy objects, resulting in force The pain will be caused by the inflammatory edema that will occur after the strain. 3. The ureteral stones will irritate the ureteral wall during the downward movement, so there will be obvious pain.