The term “slipped disc” is often thrown around. I can’t count the number of times I’ve heard somebody say:
- “Don’t bend like that or you’ll slip your disc”
- “I can’t do that because I have a slipped disc”
- “I’ve had back pain ever since I slipped my disc”
What if I told you that a disc cannot ‘slip’? I’d count on you then asking what is really happening.
What this colloquial, misleading phrase is actually referring to is a bulging disc or herniated disc. In between each of the vertebrae in your spine, you can find an intervertebral disc. They are made of two main parts:
- Annulus Fibrosis – the complex of multiple cartilage rings on the outside.
- Nucleus Pulposus – the gelatinous centre.
These discs are strong, flexible and aid in movement and shock absorption. Despite their strength, they can deteriorate over time due to injuries, bad posture, poor movement mechanics and simple wear and tear. It is important to note that disc degeneration is NORMAL as we age and does not correlate with back pain. As the cartilage deteriorates, the nucleus pulposus starts to push out and distend the disc (this is a bulging disc). If the nucleus pulposus breaks through the outer cartilage, this is a herniated disc. A bulging or herniated disc can cause nerve pain by compressing surrounding structures such as nerves.
Most people tend to view discs as fragile, easily injured and even mobile structures. This is just plain wrong. The way the disc is connected to the vertebrae creates an exceptionally strong connection making it IMPOSSIBLE for the disc to ‘slip’ even under immense load. Studies have shown that it takes 740lbs (336kg) of force to compress a disc 1mm in young subjects and 460lbs (208kg) in older subjects. Keep in mind that these studies were performed on cadavers with no co-activation of supporting muscles and ligaments. That means that when our muscles and ligaments are working, our discs are likely to be able to handle even greater forces.
I am keeping it short and sweet today. End of story is that discs are VERY strong and they do not just ‘slip’ out of place like a bar of soap in the shower.
Written by Nicholas Dimos (Physiotherapist)