The Shock Absorbers of the Spine

We have learned in traditional anatomy classes that the discs are the shock absorbers of the spine.  This is logical seeing as we know the discs are somewhat built like a jelly donut with a "squishy" jelly center.  It also makes sense as we think of the bones in the body as hard, rigid structures.  As vertebrae are bone, we would assume that they would be rigid also.


So in isolation, the disc may appear "squishy," however, we tend to forget that the discs are sandwiched between vertebrae.  What we don't often think about is how the vertebrae is constructed.  Vertebrae are composed mainly of spongy bone.  That's right, SPONGY bone!  Though the outside of the vertebrae is more rigid, the inside of the vertebrae looks like a dense sponge.  It is this property of the vertebrae that allows it to be the shock absorber of the spine. 


The structure of the disc is more fluid (or jelly like).  Fluids tend to be more difficult to compress so as our spine compresses, our vertebrae "bulge" in upon itself as the jelly pushes against the vertebrae.

Still don't believe me?  Think about it this way:  Imagine you were to eat a massive hamburger.  Think about the buns of the hamburger as the vertebrae and the patty as the disc.  The first thing you would do would be to "compress" the hamburger.  What just underwent the greatest amount of deformity (most compression?)  The "spongy" bun of course!  This is a bit over-simplified as the vertebrae aren't quiet as squishy as a hamburger bun, but it does illustrate the point.



So as your spine undergoes compression when you are running, jumping, sitting or sneezing, it is the vertebrae themselves that are the shock absorbers of the spine.