The intervertebral discs sit between the bones of the spine. They’re composed of a gel-like material (in the picture below this is called the nucleus pulposus) surrounded by a mesh of fibres (the annulus fibrosus). Whenever there’s any movement through the spine, the discs act like little shock-absorbers, to dissipate the force and protect the bones of the spine from any impact.
On either side of the disc, attaching each surface to the adjacent bone, is a cartilagenous endplate (ie, a flat circular structure made of cartilage) This not only firmly anchors the disc to the bone, but also acts as a membrane for water and nutrients to pass from the blood vessels in the bone into the disc. This keeps it hydrated and nourished.
And on top of this, there are a multitude of ligments that run over the spine and the discs. These are made from strong, tough fibres which run parallel to each other, to form a barrier with high tensile strength. These keeps the whole spine sturdy. The picture below shows the multitude of stabilising ligaments in the spine.
Seriously, discs don’t slip
All of this is simply to say that discs don’t slip. They do not slide out of place, or move around in the spine. They are firmly anchored by the end-plate and bound in by ligaments. They simply cannot slip out.
The injury that is often described as a “slipped disc”, is actually a bulge. Sometimes the annulus fibrosus (the outer rings of fibres that hold the gel of the disc contained) can be injured, and this can lead to the softer nucleus pulposus (the gel in the middle) bulging out, usually into the side of the spine. Sometimes this will put pressure on the nerve there, which causes the classic leg pain of sciatica.
Why does it matter?
Surely it’s just terminology? The pain is the same is doesn’t matter what we call it, right?
Actually, that’s not true.
We can’t see our spines. If we hurt our elbow, we would get a lot of visual information about how the injury was progressing. We would see swelling reduce, bruising go down, scratches or wounds healing, etc. In the spine we don’t get this visual information and so we rely a lot on our imagination – we have to visualise in our own minds what we think is happening in our backs. This is how our brain processes and makes sense of an injury.
And so actually the terminology we use has a huge impact on the mental image we draw up of our injury. I have had patients tell me that their “slipped disc” has moved out of their spine and they have no idea where it has gone but it’s left a great big hole in their spinal column.
The downward spiral
Now imagine how a person who thought like this would act. They would avoid anything that might challenge their “unstable”, “weak” or “slippery” spine/discs. They would be less active, they may sit/lie down/rest more. They may stop doing things they love.
All of these are things that are unhelpful to your recovering back. Research shows that movement is important to your spine and bed rest severely slows recovery.
But all this imagery of “slipped” discs will usually make someone more anxious about their back and, as we have discussed before, fear and anxiety about back pain can actually sensitise the nerves and make the back pain worse.
Good news for discs
As we’ve also discussed on this blog, discs DO heal.
So here’s what you should do if someone tells you that you have a “slipped” disc (once you’ve informed them of their mistake and pointed them to this blog – haha!):
- Don’t put yourself on bed rest
- Use paracetemol or cocodamol (not both) and/or manual therapy (like a chiropractor, osteopath or physiotherapist) for pain relief and to encourage movement
- Perform regular gentle movements in the spine in the direction that gives relief (I give my patients the McKenzie exercises)
- Be patient. Discs do heal but they take time.