causes of back muscle pain
Upper and middle back pain may be caused by: 1  Overuse, muscle strain, or injury to the muscles, ligaments, and discs that support your spine. 2  Poor posture. 3  Pressure on the spinal nervesspinal nerves from certain problems, such as a herniated disc.  A fracture of one of the vertebrae.
Low back pain may also be due to: 1  An abnormal aortic aneurysm that is leaking. 2  Arthritis conditions, such as osteoarthritis, psoriatic arthritis, and rheumatoid arthritis.  Infection of the spine (osteomyelitis, diskitis, abscess)