There are three causes of pain in the middle of the back: first, supraspinous and interspinous ligamentitis, there is a spinous process at the back of the spine, there is a long supraspinous ligament on the surface of the spinous process, when there is supraspinous ligamentitis there will be pain in the middle of the back, underneath the ligament there is interspinous ligament, when there is chronic inflammation there will also be pain in the middle of the back. Second, tumors of the vertebral body, tumors and metastases in the vertebral body will also appear in the middle of the posterior lumbar pain, the uncommon cause is the vertebral body of tuberculosis or abscess, which can be accompanied by fever, wasting symptoms. Third, women can be pelvic inflammatory disease or pelvic effusion and cause pain in the middle of the back, often accompanied by a feeling of abdominal cramping or pain in the small abdomen, ultrasound examination and CT examination should be performed to further confirm the diagnosis.