Upper back pain, also called middle back pain or thoracic back pain, is back pain that is felt in the region of the thoracic vertebrae, which are between the bottom of the neck and top of the lumbar spine. It has a number of potential causes, ranging from muscle strain to collapse of a vertebra or rare serious diseases. The upper spine is very strong and stable to support the weight of the upper body, as well as to anchor the rib cage which provides a cavity to allow the heart and lungs to function and protect them.