Slipping rib syndrome: a pain in the upper back

Although there’s an abundance of research on lumbar (back) and cervical (neck) pain and dysfunction, there’s a relative paucity of research relating to the thoracic (mid and upper back) region⁽¹⁾ This is partly due to the overall rigidity of the spine as it passes through the thoracic structure, which reduces the likelihood of injury compared to freely-moving joints undergoing a variety of loading forces. However, while the thoracic structures lack the mobility of many other joint systems in the human body, some movement is required, bringing into play a number of rib joints known as ‘costovertebral’ joints and their associated ligaments that hold them in place.

The thoracic region can move!

The thorax is comprised of a number of rigid structures, including the ribs, sternum (chest bone) and thoracic vertebrae of the spine. However, the intervertebral discs of the spine and the costal (rib joint) cartilages do enable some joint movement in the thoracic region. This movement includes⁽²⁾:

·        Flexion-extension (forwards/backwards motion) – ranging from 4^o at T1 (just below the neck) to 12^o degrees at T12 (just above the lumbar region).

·        Lateral (side-to-side) movement – this typically allows 6-7^o per vertebral segment.

·        Rotation – ranging from 9^o at T1 to 2^o at T12.

Although each individual vertebra joint motion is small, the overall result is that the costovertebral joints and ligaments combine to play a critical role in the movement required not only during the ribcage efforts and movement when breathing, but also in allowing thoracic mobility, while at the same time facilitating load bearing and stabilization⁽³⁾.

The rib-vertebrae interaction

The rib-vertebra-sternum interface is critical for correct thoracic function; it needs to be rigid enough for load bearing (to protect the lungs) and stabilisation but mobile enough to allow necessary movement. Critical to this function are the costovertebral joints and their associated ligaments (see figure 1). These joints and ligaments are poorly understood and frequently overlooked anatomical structures⁽⁴⁾, despite their abundance in the human thoracic spine (there are 108). The costovertebral ligaments are dense, fibrous ligaments, containing a large amount of elastic fibres. These fibers are able to stretch with movement in one direction yet shorten with movement in the opposite direction; this means that when subject to repeated movements, they can remain taut rather than becoming lax⁽⁵⁾.

Figure 1: Costovertebral joint and ligament structures*