The thoracic spine, which is also referred to as the upper back or middle back, is very different in form and function to the cervical spine (the neck) and the lumbar spine (the lower back). We gain mobility from the neck and lower back but the thoracic spine was designed to be extremely stable and robust to allow us to stand upright, additionally, it protects vital organs such as the heart and lungs.

As this section of the spinal column has a good deal of stability and very restricted mobility, there is generally very little risk of degeneration or injury in the upper back over time. Probably the most common causes of this type of pain are joint dysfunction and muscular irritation. There might have been an injury to a disc in the upper back like a thoracic herniated disc or degenerated disc that causes such related back pain, but these injuries are very rare.

The word "thoracic" means related to the chest, and the thoracic spine is the section of the spinal column that corresponds to the chest area consisting of:

• Twelve vertebrae in the centre of the spine with ribs connected make up the thoracic spine. If viewed from the side, this section of the spine is slightly concave.

• Each vertebra in the thoracic spine is connected to a rib on both sides at every level and these in turn meet in the front and attach to the sternum which is also referred to as the breastbone. This results in a cage (the thoracic cage) that gives structural protection for the vital organs of the lungs, heart and liver, and also creates a cavity for the lungs to expand and contract.

• The top nine ribs begin at the spinal column, curve around and are joined at the front of the chest. Because the ribs are firmly attached at the back (the spine) as well as the front (the sternum), they allow for very limited mobility in the spine.

• The lower three ribs do not join together at the front, but do function to protect the vital organs while allowing for slightly more mobility.

• The joints between the bottom thoracic vertebra (known as T12) and also the top lumber vertebra (L1 in the lower back) allow for twisting movement from side to side.

Because there is very little mobility and a great deal of stability throughout the thoracic spine, this section of the back does not have a tendency to develop common spinal disorders such as degenerative disc disease, herniated disc, spinal stenosis, or spinal instability. These disorders can cause chronic back pain but they are quite rare in the upper back.

Due to this stability and lack of movement, in most cases anatomic causes of upper back pain cannot be identified. An MRI scan or CT scan will rarely image an anatomic problem that is responsive to any sort of surgical solution for the upper back pain. Main causes therefore seem mostly to be either joint dysfunction or muscular irritation and any related treatment should be based on this diagnosis.