Degenerative Disc Disease Explained: Is It Really a Disease, and When Does It Matter?

If your MRI report mentions degenerative disc disease, it can sound frightening. The word "disease" alone is enough to worry anyone. But in most cases it describes something far more ordinary than it sounds, and it is very often not the true cause of back pain at all.

Here I explain what degenerative disc disease actually is, how it is graded on a scan, why it is so common in people with no pain, and when it genuinely matters.

First, what is a disc?

Your spine is a stack of bones, divided into regions: the cervical spine (the neck), the thoracic spine (the middle of the back, braced by your rib cage), the lumbar spine (the lower back), and the sacral area (encased within the pelvis).

Each bone, or vertebra, is a cylindrical block with an arch at the back. Together these arches form a tunnel that houses and protects the spinal cord and the nerves. Between each pair of bones sits a disc, the cushion that absorbs shock.

A disc has two parts. In the centre is the nucleus, which has a soft consistency, much like crab meat when we operate on it. Around it are many layers of lining called the annulus, rather like interwoven fabric, holding that soft centre in place. When you are upright, the load you carry is spread fairly evenly through the nucleus across the whole segment.

How is degenerative disc disease graded on an MRI?

Radiologists grade degenerative disc disease into five grades, based purely on how the disc looks on a scan.

A grade one disc is normal. The nucleus shows up bright, because it holds a lot of water, and the annulus around it appears dark.

As we age, it is normal to lose some of that water content. A grade two disc still has brightness in the middle, but less obviously so, and the annulus looks slightly thickened. By grade three, considered moderate, the central brightness is fading, the edges look blurry, and there may be a little loss of height between the bones.

Grade four is severe: the whole disc has darkened, with further loss of height. Grade five is the final stage, where the disc has fully collapsed, and you often see changes in the vertebral bodies and their end plates on either side. At this point there can be bone rubbing on bone, which is what produces inflammatory changes.

Does degenerative disc disease always cause pain?

This is the key point, and the answer is no.

A study looked at people across different age groups who had no back pain or spinal symptoms at all, and scanned them to see what would show up. Among people aged 50 and over, around 80% had some form of disc degeneration: signal loss within the disc, darkening, loss of height, or a disc bulging or protruding. A large number of people have these findings and feel nothing.

So a worn disc on a scan, on its own, tells us very little about whether you will have pain.

The clinical stages: a more useful way to understand disc problems

A far more accurate picture comes from the clinical stages of a disc problem, rather than the scan grade alone.

The early stage is the thinning and wearing of the disc lining, which can tear. In the acute phase this can be painful, because inflammatory fluid from inside the disc leaks out and stings the surrounding tissues.

The intermediate stage is one of instability. Once the lining is torn, the disc material can sometimes leak out, and the disc can feel a little unstable. Certain positions then provoke more pain. This is often why, just after a tear, sitting can be more painful than walking. If the disc material does leak out and presses on a nerve, it can cause leg pain.

The third stage is stabilisation, when things settle down. The disc lining is made of collagen, the very same material found in scar tissue. So the body lays down collagen fibres and repairs the lining. On a scan at this stage the disc often looks darker than normal, simply because it has lost some water content. That loss of water just means the nucleus is not quite as squishy as it once was. And a little dehydration in one, two, or even three discs, across a spine made of many segments, is not going to upset your function to any significant degree.

Why a worn disc is not always the cause of your back pain

This is why we have to be so careful. If you have back pain and your MRI describes disc degeneration, it does not automatically follow that the worn disc is the cause, precisely because the finding is so common in people without any pain at all.

Reading the report and assuming the disc is to blame is one of the easiest mistakes to make in spine care.

When degenerative disc disease does matter

There are situations where it is relevant. At grade five, where the disc space has fully collapsed, you can also see inflammatory changes in the bone, the bright areas on a scan. These can sometimes be a genuine source of back pain.

But before acting on that, very specific tests are needed to prove it, and we would not move to anything invasive without that proof. Equally, if a scan shows something more serious, such as nerve compression, that changes the picture entirely.

How I treat it: restoring function, not chasing the scan

Once I have excluded anything sinister on the MRI, such as nerve compression, I usually set the disc findings aside altogether. From there, treatment is about restoring your normal function, tailored to your specific and unique needs.

For this I believe in a form of physiotherapy called cognitive functional therapy. It looks at the way you move, and at any unhelpful beliefs that may be feeding the pain, gently setting those straight and restoring normal, confident movement, so you can get back to the things you enjoy.

Core strengthening exercises can help build a muscular brace that supports the segment, but in my view they get a little overplayed. There is no one-size-fits-all approach, which is exactly why I tailor treatment to what you, individually, want to be able to do. As I always say, we treat the patient, not the test result.

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