This blog of our ‘Basic Anatomy’ series of the body we have been doing discusses intervertebral discs.
There are many and varied myths out there about the risks of damage to our intervertebral discs. It can be very worrying to read labels such as ‘slipped disc’ or ‘compressed nerve’ and to not fully understand what these terms might mean. Terms such as these can have a hugely harmful effect on peoples confidence to move and use their back. Quite often in Physiotherapy practice we are fighting against some of the misconceptions and harm these terms have had on the people they have been labelled with. To be told your disc in your back is slipped out of place or that you are out of alignment will have vastly different effects on each individual that it is given to. It will depend on your experiences throughout your lifetime and your personal set of coping skills.
Here is some basic anatomy of the spine that is worthwhile reading if you have ever had a problem with your back, it will allow you to reason through your pain if it re-occurs and reduce the worry associated with it.
Intervertebral discs are the flexible but tough pieces of tissue that sit in between our vertebrae in our spines. We have one between each level and they get smaller as you go up the spine, exactly as the bones of the vertebrae do. This is because it is the lowest levels that take more weight and pressure and as you get higher up in the spine there is less weight to be managed by the discs and bones. This is their job and they do it well. Spreading load evenly across the vertebrae and ensuring that we have both a strong spine but also a flexible spine so that we can hold ourselves up and support our arms and legs but at the same time bend and move to reach the large range of directions and movements that we do. Discs are made of a strong collagen material called fibrocartilage. They have a central softer zone called the nucleus pulposa and a thicker and tougher outer rim. There are only blood vessels in the outer zone and so injury here can sometimes be felt as pain but less so from the central pulposa area. The lack of blood vessels means that healing can be slower than in other tissues in the body where blood supply is better.
As we age the water content of discs gets lower, collagen content gets higher and so the disc generally become less flexible and tougher throughout. There is less difference between the middle pulposa and outer rim area. This is a natural part of ageing and by the time we are in our 30’s this pulposa is much harder than it originally was.
Sometimes with ageing and degeneration this can lead to increased stresses and strains on the surrounding tissues due to the reduction in height of the disc as it wears and ages. It is highly variable whether you will experience pain from this process. As discussed, areas of the disc itself can produce pain but also tissues around the spine will complain if loads on them are increased too suddenly or too intensively in one particular area. This can happen after injuries sometimes when load is increased in one particular area of the back and so those tissues complain about this.
What we do know is that it is NOT the amount of wear and tear or reported ‘changes’ on MRI or X-Ray that are directly linked to the pain you may experience from your back. It is unrelated and has been proven again and again not to be confidently linked. We are still unsure what gives some people with small changes to their disc and back structure significant pain and some people with what appears to be significant changes to the intervertebral discs and back but who when asked, have little pain or trouble. What we do know is that things such as a tear in the disc or a prolapse (bulge) of the disc central material out of the usual relatively circular zone, is a normal part of ageing and will be seen in many and most people if scanned over the age of 30. It cannot be said that changes seen equals pain.
What always makes me nervous when talking about discs is the fact that it is easy to talk about them in isolation like i am doing now. Putting a lot of the emphasis on the structure it has on its own and not paying enough time and attention to its surrounding tissues and the close interactions it has with other tissues. From all the pictures you see online and in books, you would not be remiss to think that discs stand aloe between the vertebrae and that there is a gap between them and everything else. this is totally untrue. they live closely packed between layers of fascia and muscles that connect and protect the spine. This is of great importance when it comes to how we think about the discs and how vulnerable we might think they are when in actual fact it is very difficult to significantly injure your discs.
Your discs are built well. Next time you think about your discs in your back, remember that wear and tear on them is a natural part of life and it happens to us all, it doesn’t have to mean pain. They are tough tissues and are built well for their job. Look after your backs but don’t be fearful of them. It is more important to keep moving and strengthen around your backs. Your physiotherapist can give you safe exercises for you that can help strengthen and give more flexibility around your back.