https://bright-healthcare.com/causes-of-upper-back-pain/

Uscular irritation and joint dysfunction. One of the more frequent reasons for upper back pain include:
Unhealthy posture. Living a sedentary lifestyle or sitting regularly for prolonged durations with bad posture could result in structural changes to the neck and back. Deconditioned muscles may cause the spine to not align properly.
A poor lifting technique can result in injury. Improper lifting techniques can cause excess stress on the upper back by carrying a heavy object while not properly aligning the spine. Particularly, lifting and holding large objects that are above your head could cause injuries to the shoulders and the upper back.
Overuse. The overuse of the back, for example, by helping someone move in a new home or making the ceiling look better, may result in muscle strains as well as ligament sprains.
Collision or accident. Trauma from a vehicle accident (car or bike accident) and a fall at a high elevation (down steps or off of an elevated ladder) as well as a collision with a sport (football or hockey.) Lower back pain may result because of injuries to the spinal bones, muscles, spines, discs and nerves.
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