You were doing yard work all day, went to lift that last bag of topsoil and felt a pop in your back and pain down your leg. You hobble into the house, sit down, pop a few Tylenol and put some ice on it. The next day you can barely get out of bed so you go to your physician. You come out of the appointment with all kinds of information. Everyone asks what happened and you say I have a slipped disc in my back. This term has been used for a long time. Is it really possible for one of your discs to slip in your back? Is that even a medical term? Is it something that we should be concerned about?
A disc can’t physically slip. The term is not accurate. Discs are attached to adjacent vertebrae with tough, ligamentous fibers, so discs can’t “slip”. These discs are very flexible in nature and allow for spinal movement and shock absorption. However, over time discs break down with wear and tear. A disc can move, bugle and completely rupture, ultimately expanding past it’s normal position of comfort.
The term slipped disc is often used interchangeably, and most of the time incorrectly, with bulging and herniated discs, but there is a difference in the terms. The anatomy of a disc helps to understand how the they are defined.
Annulus fibrosus – is the outer layer of the disc and is composed of a fibrous layer helping protect the inner portion of the disc.
Nucleus pulposus – is the inner layer of the disc and is composed of a gel like substance.
There are many layers in your back that help protect the disc. You have muscles and multiple ligaments along your spine that are the front line defenders. If any or all of those layers are weakened the annulus is all that is left before the nucleus. When a disc bulges the nucleus pushes into the annulus and causes the disc to lose shape and push into the spinal canal. This can cause a nerve to be pinched and cause symptoms down the leg. When a disc herniates the nucleus is now not contained in the annulus and leaks out into the canal causing pain and sometimes numbness or weakness.
Looking at these two terms and knowing how they are defined tells us there is no way that a disc can physically slip out of place. The term is widely used around the health care field. We just need to understand what it is being used for.