Degenerative Disc Disease (DDD)
Written by Chris Heywood - MSc BSc (Hons) MCSP HCPC reg
Physiotherapist
Over my 23-year career, I've encountered countless patients who come to my clinic in a state of panic after being told they have, or might have, Degenerative Disc Disease (DDD). This term often causes unnecessary alarm due to common misunderstandings. Let’s clarify what DDD really means and how concerned you should be.
DDD sounds bad - but how bad it is really?
​Degenerative Disc Disease (DDD) is a phrase that originated many decades ago to describe what is more commonly known as 'ageing' of the intervertebral disc. Despite being very common in adults, it is very difficult to speculate the exact occurrence rate due to broad variations in published research. What we do know is that the older we get, the more chance we have of developing it, HOWEVER, advancements in research are now suggesting that up to three quarters can actually be attributed to genetic factors.
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It's crucial to understand that DDD is not a disease in the conventional sense. The term "disease" can create unnecessary worry, especially in those prone to anxiety. Many professionals believe the stigma associated with such terminology can be harmful. Let’s dispel some common misconceptions about DDD. For this discussion, we’ll concentrate on the lumbar spine (lower back). The principles can generally be applied to the entire spine.
Intervertebral Disc Anatomy
Intervertebral discs consist of two main sections, an outer annulus and an inner nucleus pulposus. They are connected to the surrounding vertebrae by 2 end plates, one on the top and one on the bottom. They are located between the vertebrae in our spines, separating the large bony areas at the front of the spine - see below.
The lumbar vertebra, end plates, nucleus pulposus and annulus. For reference, the tummy is to the left-front side and the back is towards to the upper right.
The Anulus Fibrosus: This outer structure consists of between 15 to 20 sheets of fibrocartilage (Type 1 & Type 2 collagen) that we call lamella. These are a type of strong, inelastic protein similar to those that make up your ligaments. In cross section they look very similar to a sheet of plywood, having a unique design where by each layer runs at 120 degrees when compared to its neighbour. This type of structure has a naturally high resistance to tension (stretching force) however a low resistance to compression (squashing). Between these layers is an elastic coating which helps the overall disc structure adapt to different loads and forces and reduce the chance of injury and/or failure.
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The Nucleus Pulposus: This viscous (thick) liquid, similar to the elastic coating in the annulus described above, is best thought of as like the soft centre of a jam doughnut. Made up from a mixture of water, prostaglandin and collagen , the nucleus helps to maintain the outward pressure needed to support the compression loading through the disc structure.
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The Bony End Plates: There are two cartilaginous end plates which sit on the top and bottom of the individual discs. They are joined at the inner edge of the annulus, to the disc, and then merge to the bony surfaces of the vertebra, above and below. They essentially anchor the disc and keep the annulus and nucleus contents separate from the vertebral body. ​
How Does the Intervertebral Disc Work?
The best way to think of the disc is to imagine it's role within the spine as a 'spacer' between the adjacent vertebrae, as well as a 'shock absorber' of sorts. They undergo a continuous cycle of repair and destruction, facilitated by the exchange of nutrients and waste. In childhood, discs have a direct blood supply, but this changes around age 18-20, relying instead on tiny channels in the end plates. This system remains effective for the most part but can fail, potentially leading to DDD.
When the balance of this system falters, the disc’s outward pressure decreases, and the annulus loses its resistance to compression and torsion. This can lead to minor tears and structural changes, potentially causing pain, especially if these changes occur near nerve supplies. The nerve supply to discs, how this relates to pain and how this can change in certain situations is a continuous area of debate in the spinal world.
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It is vitally important to understand that disc degeneration in its own right is considered NORMAL, and having these changes DOES NOT automatically mean you will get pain.
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Degeneration only becomes an issue when the disc, or other structures, have been altered in a way that gives rise to pain by some mechanism. Changes in the disc can often overload other structures as well, such as the soft tissue or joints, and it may in fact be these structures that eventually give rise to the pain, not the disc itself. In reality, because we do not have a pain scanner yet, we can not always be sure of the exact pain generator in every patient. Scans look at anatomical changes, not whether of these changes are giving you pain or not. This is why it is imperative that scan reports are interpreted by those clinicians with the ability to interpret and then cross match these against a patients symptoms.
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As a result of pioneering research projects such as 'EuroSpine' and the 'Genodisc project', and others building upon these, it is now thought that up to 70% of 'degenerative disc' processes can be explained by our genetics, meaning that environmental factors may play much less of a roll than previously thought. This is especially true in the cases of younger patients (sub 30 years) where we would not normally expect to see these 'age related' changes.
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It may also explain why we see so many families, through varying generations with similar back pain presentations. As clinicians, we picked up on this a long time ago but it is only in recent years that we are beginning to see the advancements in research backing this up.
What Does DDD Feel Like?
When it comes to Degenerative Disc Disease (DDD), the symptoms can be tricky to pinpoint. Interestingly, it's quite common for people to have degenerate discs without experiencing any back pain. In fact, about 30% of the UK population would show significant changes in their spine if scanned, but many of these individuals don't have, and may never have, any symptoms of back pain. It might sound strange, but that's the reality we deal with!
What Causes The Pain?
While sharp pain can sometimes be caused by annular tears due to the direct nerve supply at the back of the disc, more often than not, the pain arises from other structures. These could be overloaded or inflamed facet joints, compressed nerves (from disc bulges), or mechanically irritated areas (such as in spinal stenosis, spinal instability, or poor muscle control). These issues often result from the reduced health of the disc or the ways your body compensates for it. The only way to definitively identify the presence and extent of DDD is through an MRI. However, since MRIs don’t necessarily indicate the exact source or presence of pain, there needs to be a solid clinical reason for ordering the scans.
Diagnosis And Treatment
In many cases, pinpointing the exact anatomical source of pain is impossible. However, this doesn’t usually affect the effectiveness of treatment, as long as you're under the care of a skilled specialist or expert therapist. Without any signs of serious pathology or injury (Red Flags), exercise is widely recognized as the best way to combat most forms of back pain. This approach is not only supported by a wealth of evidence but also widely acknowledged in the medical community.
Finding The Right Exercises
One challenge we face is determining which exercise is best for each individual. There are numerous variables that can influence back pain, from the way our brains process and control pain to subtle differences in the root causes of the problem. As a result, we may never identify a one-size-fits-all solution. However, with the right guidance and a tailored exercise plan, you can manage and alleviate your back pain effectively. If you’re experiencing back pain and suspect it might be related to DDD, don’t hesitate to reach out to our specialists. They can provide a personalized treatment plan to help you live a more comfortable and active life.
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