Our spine is an amazing structure. It’s assembled in such a way that it supports both stability and mobility. The key to the spine’s function is the series of vertebrae that it’s composed of. In this article, we’ll take a closer look at one specific part of those vertebrae that make up the spine, the spinal discs. We’ll explore spinal disc function, disc dysfunction, and yoga.
A quick review of vertebral anatomy
Before we dive into the spinal discs specifically, let’s do a quick review of spinal anatomy. Our spine is composed of three main sections. The cervical spine includes the seven vertebrae in our neck. The thoracic spine includes the 12 vertebrae between the base of our neck and the top of our low back. Our lumbar spine includes the bottom five vertebrae of our spine. With some rare exceptions, most of us have a total of 24 vertebrae that make up our spine.
Vertebrae are composed of several parts. Each vertebra has a large round body with three bony projections coming off of it. One of these bony spines heads out to the back (posteriorly). That is the spinous process. The other two point out to the right and left sides (laterally). They are the transverse processes.
In each vertebra, there is a hole immediately behind the body of the vertebra and in front of the spinous process called the vertebral foramen (hole in a bone). When the vertebrae are stacked in a column, that space is where the spinal cord runs. There are also spaces to each side where the nerve roots exit as they come off of the spinal cord and run to other areas of the body. Each vertebra meets the one above and below close to the transverse processes to create the facet joints. The facet joints are where the vertebrae articulate with one another bone to bone and allow our spine to move. As we’ll see, the discs are also a place where movement occurs.
Vertebral disc function
One reason why our spine functions as it does is because of how each of our vertebrae is connected to the vertebrae above and below. Between the body of two vertebrae is an intervertebral disc. Each intervertebral disc is composed of two main areas. It has a fibrous outer ring called the annulus fibrous. Within the annulus fibrous is the fluid-filled center called the nucleus pulposus. When all our spinal discs are healthy, they function to maintain the space between vertebrae. The fluid-filled nucleus gives the intervertebral disc the pressure to create space between the bony vertebrae. This allows our spine as a whole to absorb force from different directions and then distribute it.
Types of intervertebral disc dysfunction
When our spinal discs are dysfunctional, however, they can be dysfunctional in several different ways. You might have heard some of those terms. A bulging disc happens when the vertebrae above and below the disc compress it so that some of the disc pushes out, or bulges, between the two bones. When there is damage or a weakened area in the bulge, we call that a herniated or a prolapsed disc. If the vertebral disc tears so that the tear reaches all the way to the nucleus pulposus, we call this a ruptured disc. This is the most serious type of dysfunction. When the nucleus pulposus tears and fluid leaks out, the vertebral disc can no longer maintain space between vertebrae.
Other disc dysfunction
You might also have heard the phrase “slipped disc.” This term is a misnomer. Regardless of what kind of intervertebral disc dysfunction you experience, the whole disc does not slide or slip out. It’s just an area of the disc that either bulges out or ruptures. This phrase may be indicative of the description used by people when a disc herniates, however, it should not be taken literally. Additionally, you may have heard the phrase degenerative disc disease. This is a broad way to describe all of the reasons discs degenerate in their function. It most often refers to age-related disc degeneration that causes pain. Sometimes this is associated with a loss of space and/or a general degeneration of the disc material which happens to everyone as we age. It’s more of a concern when this happens at a faster rate than the natural aging process.
Results of disc dysfunction
When there is an intervertebral disc dysfunction (a bulge, herniation, or rupture) and part of the disc presses on a nerve root, it’s usually painful. You might experience sensations of tingling, numbness, and/or generalized pain. Additionally, there may be some loss of function. It depends on the situation. It’s also possible for discs to bulge or herniate and not press on a nerve. In that case, you may not even know that you have a bulge or herniation and it may never cause any pain or problems.
Why does disc dysfunction happen?
Dysfunction can happen as part of chronic long-term wear and tear from repetitive activities. Or it can simply be a result of aging. We are all drying out as we age. Disc dysfunction can also happen as a result of acute accidents or injuries. Those kinds of injuries could include things such as picking up a heavy object with straight legs.
Disc dysfunction and yoga
While it’s possible for disc dysfunctions to happen anywhere along the spine, the most likely spot for them to show up is in the lumbar spine. Specifically, L4-L5 and L5-S1 seem to be the most vulnerable to herniation (Dydyk et al., 2022). This is due to the shape and orientation of the vertebrae in the lumbar spine. They’re oriented with about a 45-degree tilt downward.
Dysfunction of the intervertebral discs comes up the most in two categories of postures in yoga. This is due to the most common location and direction of disc herniations. The most common place for disc dysfunction in yoga to come up is forward bending. The other place where disc dysfunction could likely come up in yoga is in twists. In some cases, disc herniations might also come up in deep backbending.
A large percentage of herniated discs resolve on their own within a few weeks (85-90%; Dydyk et al., 2022). So it’s possible that you may have students arrive at yoga class who previously experienced a herniated disc, but are not acutely feeling pain. If someone has previously experienced disc dysfunction and is returning to yoga, they should have clearance from their doctor to resume a yoga practice. When returning to yoga after disc dysfunction, use particular caution when working with forward bends and twists. Consider not taking postures close to ends of range of motion, especially with older practitioners.
I talk about forward bending specifically and disc herniations in my article Practicing Yoga With A Herniated Disc. The main thing to keep in mind here is that forward bending has the potential to make a disc herniation worse. This is because in forward bending, we flex the spine which can push a disc herniation back towards a nerve root and cause pain. So when we forward bend, it’s important to focus on flexing from the hip joints. Minimize any flexing of the spine. You can even work with a little intention of extending the spine as you flex at the hip to help keep the forward fold happening from the hips. This will likely mean you don’t reach as far in your forward bend as you might otherwise.
As I mentioned earlier in this article, the lumbar spine is generally more susceptible to herniation. This means that it is important when twisting not to overdo the amount of twist that happens in our lower spine. Remember it’s the thoracic spine that’s best suited for twisting anyway. So if you have concerns about disc dysfunction in yoga, be mindful of where your twist is happening. You can even allow the pelvis to rotate some to reduce the amount of pressure the twist puts on the lower vertebrae.
This third category of postures where you might want to use extra caution when you’re concerned about disc dysfunctions in yoga is deep backbending. We ask a lot of our spine when we do deep backbending. But, like forward bending, backbending starts at the hip joints. Our biggest restrictors to backbending are usually the hip flexors. Tension in the hip flexors can restrict how much movement we get in the backbending direction from the hips. And if we don’t take the time to open those hip flexors to allow backbending to start there, we can overdo the bending from the lumbar spine. And that can affect the health of our lower spine generally, as well as cause additional problems if we have existing disc dysfunctions. So, it’s important to start our backbend from the hips and pay attention to distributing the bend through the whole spine.
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Dydyk, A.M., R.N. Massa, and F.B. Mesfin. Disc Herniation. [Updated 2022 Jan 18]. In: StatPearls [Internet]. Treasure Island (FL): StatPearls Publishing; 2022 Jan-. Available from: https://www.ncbi.nlm.nih.gov/books/NBK441822/.
Jeng, C.M., T.C. Cheng, C.H. Kung, and H.C. Hsu. 2011. Yoga and disc degenerative disease in cervical and lumbar spine: an MR imaging-based case control study. Eur Spine J. 20(3):408-13. doi: 10.1007/s00586-010-1547-y.