What are discs and what are slipped discs?

Intervertebral discs sit between the bones in your spine (vertebrae) and act as shock absorbers.  They also contribute to the flexibility of your spine.

Spinal Anatomy taken from Functional Anatomy of the Spine Middleditch & Oliver

Discs sit in the anterior (front) part of your spine so you can’t feel them through your skin.  When you touch your spine you are feeling the Spinous Processes, which are the pointy bits of each vertebra shown on the picture above.

There are a few components of the disc which are useful to understand. At the top and bottom of each disc is the vertebral end plate, which grows into the adjacent bone and helps provide nutrition to the disc.

Anatomy of intervertebral discs taken from Functional Anatomy of the Spine by Middleditch & Oliver

If you take a horizontal slice through a disc you can see outer rings.  This is called the annulus fibrosus.  The centre of the disc is made of a thick gel called the nucleus pulposus.   This structure allows your discs to stretch and move.

The outer part of your discs are supported by several of your spinal ligaments, which join bone to bone and also grow into the annulus fibrosus.

What’s a slipped disc?

Your discs don’t actually slip anywhere, they are held firmly in your spine so they cannot come out of place.   They can become injured, irritated or change shape which may lead to pain.  Interestingly MRI studies have shown that many people have disc ‘injuries’ with no pain or stiffness!

We think that several different things can happen to your discs.

Firstly the outer annulus can become torn.  This may lead to inflammation and then to pain and muscle guarding.

Secondly the disc may change shape and bulge outwards.  This can happen anywhere around the edge of the disc but is most common towards the back and side.  A disc bulge can be very small or more substantial.  They can also change depending on your position.

If a disc bulge is close to a nerve root it may irritate the nerve or squeeze it.  This can cause pain, pins and needles or numbness along the path of the nerve.  A famous example of this is sciatica.

Disc injuries are very common. Most people make a full recovery with conservative care such as exercise, stretching and manual therapy (including osteopathy).