There are 25 bones in the spine – these are called 'vertebrae' (when referring to more than one – a single spinal bone is called a 'vertebra' – the word is derived from the Latin for 'to twist'). In between one vertebra and the next is a small disc (an 'intervertebral disc') which acts as a form of cushion during movement.
The spinal cord, which connects the brain to other parts of the body, runs through the middle of the vertebrae, in the 'spinal canal', and an additional role of the discs is to allow enough room for major nerves to come out of the spinal canal.
Each intervertebral disc comprises an inner sac of gel-like fluid called the nucleus and an outer ring (called the 'annulus' – Latin for 'ring') composed of denser fibrocartilage.
The inner sac in young children and young adults has a high water content (80% at birth), but over time this water content decreases, so that from middle age the intervertebral discs become thinner and slowly lose some of their cushioning and protective properties. This can also lead to other problems with the spinal discs which can cause back and leg pain.
Even though this process is also referred to as 'degenerative disc disease' it is not really a disease as such, simply a normal 'wearing out' of the discs with age. The term 'degenerative disc disease' is also applied to spinal disc problems that occur either along with, or independently of the normal ageing process.
As outlined above, degenerative disc disease is unfortunately an integral part of the ageing process. There are however a number of factors which are linked with disc with disc degeneration, such as…
- Being overweight.
- Bad posture.
- Genetic factors – if for example there is a family history of early onset disc degeneration.
- Strenuous physical lifestyle (i.e. manual work involving lifting weight and/or active sports participation).
- Sedentary lifestyle (i.e. sitting for long periods of time).
- Other medical conditions affecting the spine, for example scoliosis or osteoarthritis
- Prior spinal injury / infection.
Degenerative disc disease also tends to affect men more than women.
Chronic disc degeneration is normal, and likely to be painless.
However, acute degeneration of a disc (disc prolapse or disc tear – links) can be acutely painful and may result in pressure on exiting major nerve roots. Most acute disc accidents resolve spontaneously over time, but some do require medical or surgical treatments.
Tests / Diagnosis
In most cases, expensive imaging is not needed, but if significant nerve root compression is suspected, MRI or CT scanning may need to be performed.
CT/MRI scans (this will reveal any other factors such as bone spurs – 'osteophytes', evidence of spinal stenosis, fracture or presence of tumours).