The discs in the spine are well attached to the vertebrae directly above and below them. They act as a cushion for shock absorbing, and they can be twisted and squashed to allow for movement through the spine. A good analogy for their anatomy is to imagine a jam doughnut, where the outside is tougher than the inside, which is somewhere between a liquid and a solid. The doughnut is the disc: the thick dough is the fibrous ring outside, and the jam is the soft nucleus.
If the discs are so tightly fused to the bones, then they can’t possibly “slip”. This is true, so the term “slipped disc” is completely misleading. Saying that the disc is “bulging” or “herniated” is more accurate. What really happens is one of three things:
- The outer edge of the fibrous part is irritated locally
- The fibrous part is weakened somewhere, and the nucleus pushes against it, causing a bulge
- The fibrous part ruptures, allowing some of the nucleus to leak out of the disc
Not only do discs not slip, but they don’t always cause pain when they bulge. Imaging repeatedly finds disc bulges in patients who have no symptoms at all. A study from 1994 showed that 64% of their examined participants had at least one disc bulge without any pain at all.
It is so important to remember that pain is not a reliable indicator of tissue damage. I have seen a patient in so much pain that he couldn’t bend down to take his shoe off, or even stand up out of the chair for 40 minutes; who was then symptom free after one treatment. Likewise, I have had patients with lower grade symptoms that take much longer to relieve.
Further research also shows that although ageing does increase wear and tear on the discs, the likelihood of discs bulging reduces in our elderly years. This is because the discs dehydrate over time (they lose height and so we shrink), meaning they are less flexible and therefore less able to bulge. This does make way for other causes of back pain such as osteoarthritis as the spinal joints become closer together and friction between the two surfaces accelerates wear and tear. But keeping active is the best way to minimise the effects of inevitable ageing: don’t be fearful of using your back through its full range.
Nerves can be irritated by a bulging disc, notoriously causing shooting pain, numbness, or pins and needles. If this happens to the sciatic nerve, we would call this sciatica. I’ve written about sciatica in more depth here, and the mechanism is the same for any nerve irritated while leaving the spinal cord.
Discs can be irritated by a number of things, such as overuse of one level in the spine due to restriction above or below it; and misuse or trauma, such as heavy lifting with poor form. Your osteopath will be well versed in these kinds of symptoms. We can help treat the symptoms for short term relief as well as addressing the underlying cause. We can also provide advice for changing how you do things that may be aggravating it, such as lifting or sitting at a desk that is poorly set up for you.