The sudden appearance of back pain may be due to the following causes: 1. peripheral nerve lesions, such as cold in the back, or the presence of degenerative changes in the spine, resulting in compression and stimulation of the posterior branch of the spinal nerve, then the sudden appearance of back pain. 2. transient muscle spasms, such as patients sitting and standing for a long time with their heads down, or have a bad sitting posture, when the patient suddenly get up and stand upright, stretching. 3. 3, back-related injuries, such as sudden violent blows to the back, or intense activity, resulting in back-related muscle strain, resulting in back pain. 4, thoracic and abdominal organ lesions, such as heart-related lesions, may cause back pain in the left shoulder. The lesions of the aorta, such as aortic coarctation, may cause pain from the middle of the back to the lumbar abdomen; the lesions of cholecystitis may cause pain on the right side of the shoulder and back; the lesions of pancreatitis may cause pain on the left side of the waist and back.