Feb 12, 2009
What Causes Herniated Discs?
Here's a question about herniated discs I received the other day that touches on a hot button topic for many people...
Ever since my MRI came back showing herniated discs at L3-4 and L4-5 I've been reading everything I can find about disc degeneration.
One article I read said that disc degeneration is just part of the aging process. If that's true, why doesn't everyone my age (over 50) have herniated discs?
What are your thoughts?
Thanks for writing.
You've raised a very interesting question.
Is aging a primary cause of herniated discs?
Since you didn't mention a particular article, I took the liberty of hunting up a similar statement to use for the sake of illustration...
"Although daily activities may cause the nucleus to press against the annulus, the body is normally able to withstand this pressure. However, as the annulus ages, it tends to crack and tear." 
Although the paragraph I pulled this quote from does not come right out and say that age is the cause of herniated discs, anyone reading the above could very easily make that assumption.
The average layman (such as myself) will undoubtedly conclude that cracking and tearing of the annulus (the outer ring of the disc) is strictly related to the aging process and therefore, aging must be the cause of herniated discs.
However, if you're a natural born skeptic with a nasty habit of questioning everything you read, you may begin to wonder, "If age is the cause…"
- Why doesn't everyone past a certain age have herniated discs?
- Why don't all of our discs degenerate and rupture?
- Why do some 20 year-olds have herniated discs while many 60, 70 and even 80 year olds do not?
- And why is it that Nelson and others have produced research showing that discs can heal and the bulges resorb. 
Have these doctors found the fountain of youth? Or is the age explanation simply wrong?
My guess is the age assumption is not exactly wrong. It is merely an oversimplification. The above writer (or his editor) was probably attempting to be brief and simply picked what he thought was the best example (i.e., aging) from among the various causes of disc degeneration.
So, while the above quote may be technically correct, it is obviously incomplete and that makes it a bit inaccurate. There must be other factors involved.
For example, McGill writes...
"Herniations tend to occur in younger spines (Adams and Hutton, 1985) … Older spines do not appear to exhibit classic extrusion of nuclear material but rather are characterized by delamination of the annulus layer and radial cracks..." 
So we see that while age does seem to correspond to cracking and tearing -- as our original quote indicated -- this does not necessarily lead to disc herniation.
Instead, according to McGill, it is younger spines that are more inclined to rupture.
To further clarify things, McGill lists what I believe to be a more insidious cause of herniated discs (emphasis mine)...
"Epidemiological data link herniation with sedentary occupations and the sitting posture (Videman, Nurminen, and Troup, 1990). In fact, Wilder and colleagues (1988) documented annular tears in young calf spines from prolonged simulated sitting postures and cyclic compressive loading (i.e., simulated truck driving)." 
So, based on this additional information, it would seem that -- while age does appear to take a toll on intervertebral discs -- herniation appears to be caused by other more destructive factors such as prolonged sitting, compressive loading, and inactivity.
Summation and Hypothesis
Aging is obviously a factor in any degenerative condition. As people get older they begin to notice that their skin, hair, joints, bones and other tissues aren't what they used to be.
So it stands to reason that older people, to a certain degree, are going to be more susceptible to disc degeneration.
However, I believe it's incorrect to make aging the primary scapegoat.
Instead, I believe that inactivity and compressive loading are the real culprits and that age is merely a supporting cast member (along with other possibilities such as smoking, poor diet, and external trauma).
Suffice it to say, I believe we do ourselves a disservice to focus on age as the main cause of herniated discs, especially when there is research available that indicates otherwise.
Table of Contents for this series:
- What Causes Herniated Discs?
- The First Step in Repairing Herniated Discs
- Compression Loading and Herniated Discs
- Twisting and the Herniated Disc
- My Philosophy of Disc Rehabilitation
About the Author
Rebuild Your Back
Rebuild Your Neck
The Pain Relief Manual
1. Orthogate, Lumbar Disc Herniation (eOrthopod) Friday, 28 July 2006
2. Nelson, B. The Herniated Disc: New Concepts and Treatments. Physicians Neck & Back Clinics 
3. McGill, S. Low Back Disorders, Evidence-Based Prevention and Rehabilitation, 2nd Edition. (p. 44-47) Human Kinetics (2007)
Last Updated: Feb 11, 2009