The normal human spine is capable of many movement possibilities, specifically side bending, rotation, flexion and extension. Postural changes resulting in reversible curves happen all the time; bending over to pick something off the floor, reaching up high with one arm, carrying a baby on one hip. Even when these postural changes become habitual, they can be reversed so long as bony changes have not occurred (Hawes and O’Brien, 2006). Examples here might include a lower spine curvature as the result of a leg length difference that resolves once a heel orthotic is used, or the temporary altering of posture that results from muscular contraction after an injury. The hallmark feature of these curvatures is that once the source of the curve is removed, the spine resumes its normal position. By definition, a functional scoliosis resolves when the person lies down or bends to one side (ibid).
On the other hand, a structural scoliosis, either idiopathic or congenital in nature, does not go away when the spine is bent to the side, prone or supine (laying on the front or the back). The spinal segments involved in the curvature have lost some of their flexibility (Hawes and O’Brien, 2006) and so are resistant to a change in position.
Interestingly, Hawes and O‘Brien (2006) believe there is potentially less separation between the definitions for structural and functional scoliosis than recent literature might suggest. In other words, what starts out as a functional scoliosis as a result of postural asymmetry may become structural if left untreated for a long period of time. At the other end of the scale, in a structural scoliosis as long as the spine still has significant growth to do before reaching skeletal maturity, there is potential for reversal of the curvature, sometimes completely. Once the spine has reached its full growth potential this reversal of curvature is not possible, however there is still flexibility (and therefore possibility for better posture) within the spinal column except at the apex of the curve.
On a personal note, that possibility for change within the boundaries of the curvatures of the scoliotic spine is what both excites and encourages me. I have seen young people in their twenties work hard to make postural changes that have them holding their spines in a less rotated and laterally shifted position. My middle aged and older clients are able to strengthen their core musculature as well as spinal stabilizers in order to stand straighter and reduce the tendency to ‘collapse’ into the curve. And of course, unless there are other limiting factors, those who are still growing have the most possibility of altering the trajectory of their scoliosis.
Here’s to possibility!!