What Is A “Slipped Disc”
When someone hurts their back, they sometimes think that they have “slipped their disc”. What they are referring to is the soft squishy structure located between each bone or vertebrae in their spine. Your discs act to absorb compressive and rotational forces through your spine. A large part of your discs are made up of a type of cartilage as well as water. They are divided into 2 main parts: an inner “nucleus pulposus” and an outer ring layer, or “anulus fibrosus”.
How Discs Are Injured
When someone “slips their disc”, their disc does not actually slip out from between their vertebrae. One way to injure your disc is to bend forward and lift something off the ground. However, the cause can often be less obvious or sudden. In many patients, their discs become injured slowly over a long period of time of months to even years, due to repeated lifting, bending or simply bad posture. One of the worst positions for your discs is sitting and bending forward to lift something off the ground. This puts almost 3 times as much pressure on your discs as standing does. Sitting alone places more pressure on your discs than standing. The least stressful position for your discs is usually laying down on your back.
When a disc injury begins, the inner part of the disc can start breaking down because of stress and tension. This can put stress on nearby soft tissues and joints leading to the start of symptoms. This stage is referred to as, “internal disc derangement”. Think of a jelly doughnut – this is as if the jelly or nucleus inside the doughnut starts going bad.
As your disc continues to break down, it can begin to lose height and get compressed down. An example would be like squishing a water balloon. As the disc is getting squished, the cartilage in the top and bottom parts of the disc begin to break down. This loss of disc height as well as cartilage erosion can lead to pain and discomfort.
Next, the outer annulus layer, or doughy part of the doughnut, can start tearing and the middle jelly can start to leak into this outer layer. Your discs have nerves located in this outer layer and as the tear reaches the outer part of the annulus, pain signals are sent to your brain to feel pain.
As a disc injury progresses, the outer layer can start to bulge out into your spinal canal and irritate your spinal cord. This is called having a disc bulge or prolapse.
Afterwards, as the bulge progresses, the outer doughy layer can tear open and the inner jelly or disc material can start to leak out, or extrude. Once the jelly leaks out, it can travel down your spinal canal and put pressure on your spinal cord, causing more serious problems. This stage is referred to as sequestration.
Treatment for disc injuries usually starts with conservative care, such as visiting your physiotherapist or your chiropractor. If an injury progresses to the point where someone has considerable leg pain or numbness in one or both legs, numbness around their pelvis or even bowel and bladder problems, then surgery starts to become the more likely treatment option.
So a disc does not actually ever “slip” out of place, but instead the disc will gradually break down. It can then possibly leak into your spinal canal causing pain and other symptoms.