• Lucy Adie

OsteoBlog: The Spinal Disc

The 33 vertebrae that make up the spinal column, serve to protect the spinal cord and enable movement about a bony axis in flexion, extension, side bending and rotation.

A spinal segment consists of two vertebrae, with a disc in between anchored to the bone via their cartilage end plates and stabilised by ligaments.

The front portion is the load bearing area with solid vertebral bodies stacked on top of each other cushioned by the discs. There is no disc between the 1st and 2nd vertebrae in the neck and the last disc is between the bottom lumbar vertebrae and the sacrum.

Together, the intervertebral discs make up about one quarter of the spines length. The discs are thinnest at the neck and get thicker towards the lumbar region (10mm), reflecting the load bearing properties at that region.

Below is a good diagram showing the anatomy of a spinal segment:

As we have stated, the discs are sandwiched between the vertebral bodies forming fibrocartilaginous joints. They restrict excessive movement and absorb the compressive forces of daily activities.

The discs are composed of a tough outer fibrocartilage called the annulus fibrosis. The fibres are arranged in a cross hatch pattern concentrically to absorb rotational forces. There is no vascular supply to the annulus so it relies on the cartilage endplates for nutrients. This also means that healing time is unfortunately slow.

The annulus encloses a gelatinous core called the nucleus pulposus composed of 80% water with glycoproteins, and functions to redirect stress and store energy.

The water content diminishes with age and during the course of the day, which is why we lose height as we get older and we are always taller in the morning! Good hydration, therefore, is very important for disc and overall spine health.

So what goes wrong?

The nerves that supply your torso and limbs branch off the spinal cord at various levels and exit through gaps between the bones called foramina. They pass right next to the disc and so any discrepancy in the disc surface can cause irritation and pain at these nerve roots.

Sudden movements can cause the outer annulus to become strained or even tear, and this may cause the disc contents to bulge slightly, further irritating the nerve roots.

The term 'slipped disc' is a really inaccurate way of describing damage to the disc.

A disc does not 'slip', but the contents can burst out due to traumatic forces or as a result of degenerative changes. The process is called a herniation. This can cause irritation and compression of the spinal nerves causing pain in the back and limbs, muscle weakness and sometimes cord disruption.

As we age, the discs lose fluid and can dry out causing cracks and fissures to appear, weakening the annulus. The commonest disc to herniate is L4/L5 in the low back, accounting for most surgical spine repairs in males aged between 40-45.

So the discs dry out and lose height, and the spaces between the vertebrae close up a little. The spinal ligaments become a bit more slack and so stability is compromised. In response to this, the body forms bony spurs (osteophytes) in a bid to strengthen the area and these can further irritate the nerves. These signs do not always produce pain and dysfunction. This is why MRI scan results are not always indicative of the cause of back pain.

The term spondylosis refers to several processes that can occur in the spine. This includes osteoarthritis of the facet joints, osteophytic formation, and slipping of the vertebrae forwards as a result of facet breakdown. These all contribute to disc degeneration but there are further risk factors that play their part:

Age, obesity, smoking, poor postures, previous traumatic injury and some doctors believe there may be a genetic component too.

We cannot reverse the degenerative changes that occur but there are a lot of treatment options available:

Osteopathic manipulative therapy

Soft tissue release

Non steroidal anti-inflammatory drugs

Steroid injections

Surgical procedures to fuse the spine or remove part of the discs

You can visit an osteopath if you are suffering with back pain. They will take a full history of your complaint and examine you thoroughly including orthopaedic and neurological exams. They will be able to refer you to your GP if they think something serious is going on or you need drug treatment or surgery.

For further resources have a look at the following sites:


For Osteopathy in High Wycombe and beyond, call Lucy from OsteoFusion on 07833 321604 or visit

Thanks for reading.

#spine #intervertebraldiscs #cartilageendplates #vertebrae #spinalcolumn #annulusfibrosis #nucleuspulposus #nerverootirritation #degenerativediscdisease #discherniation



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