If you ask most people, they will likely say that the most common cause of low back pain is a pulled muscle or arthritis. Now these can both be present in people with low back pain, but is it the cause? What causes musculoskeletal pain in the first place? I am glad you asked! Your nervous system controls your ability to feel pain, so whenever you move the “wrong way” and feel that sharp pain in your back, your nervous system is controlling that. Nerves are typically irritated from two different mechanisms: pressure and tension. Think of a nerve as an elastic hose with water flowing through it. Apply too much pressure on the hose, and the water will start to back up. In this way, a nerve will give off a pain signal to your brain in response to too much pressure when its blood supply is compressed (7). Nerves also have elastic properties as well, like a rubber band. If you stretch out a rubber band too far, it can become overstretched. Similarly, when a nerve is stretched too far or too quickly, the nerve will send a pain signal to your brain (6). So, in order to understand the cause of low back pain, we need to understand what can cause too much pressure or too much tension on the nerves in your low back.
The most common source of pressure for the nerves of the low back is the intervertebral disc. In general, about 40% of low back pain is caused from the disc itself (2). Think of the disc as a jelly donut. If you take a needle and poke a hole in one side of the donut and push down on the opposite side, jelly will be squeezed out the hole. Now this is not saying that your disc has holes in it. This means that applying pressure on one side of the disc can cause the “jelly” within the disc to move toward the opposite side. For instance, if I stand up and lean forward to touch my toes, pressure is applied on the front of the disc that pushes the “jelly” within the disc toward the back (1, 5). One of the most common ways a disc can get injured is lifting an object while bent and twisting. The twisting motion in addition to the pressure change from the forward bending motion can cause the disc to become sprained, which could lead the disc to “bulge” slightly (4). That “bulge” then can apply pressure on the nerves in the low back or the inflammation from the “bulge” can cause irritation to the nerve (3, 9).
I would like to highlight one point before we move onto tension causing nerve pain. One thing I hear from patients frequently is, “I thought that when my disc bulges, that I needed to get surgery.” While surgery is an option for some people, a disc bulge is not an automatic sentence for surgery. Think about how simple it was for pressure to change in the disc, just from a forward motion. The same can be true for removing that pressure on the back of the disc. Bending backwards can help decrease pressure on the back of the disc. Here is a link to a simple exercise that you can do help with low back pain that is caused from the disc.
https://www.facebook.com/wcccpc/photos/a.1804572056340833/1807729519358420/?type=3&theater
Have you ever thought “my back is really tight, I should probably stretch my hamstrings.” So then you stretch your hamstrings and the stretch feels great directly after, but after a while you start getting sore. The reason for this is because the hamstring is not the only tissue you are stretching. You are also stretching the sciatic nerve (6). Remember from earlier when I said that nerves respond to tension? Movements, such as where your leg is straightened and you lean forward to touch your toes, add tension on the sciatic nerve (6). These movements do not always cause pain for people, but if you already have low back pain, avoid stretching the hamstring stretches for now.
Now that you have read through this article, what is the most common reason we get low back pain? The answer is: nerve irritation. The nerve irritation can be from increased pressure on the nerve from the disc itself, from chemical irritation from the disc, or from a tension issue involving the nerve itself (2, 3, 8). If you have low back pain and you are reading this, don’t worry. Most low back pain cases can resolve after a 4-6-week treatment plan including spinal manipulation and exercise therapy. Some bouts of low back pain take less than 4 weeks, some take longer than 6 weeks, but that is dependent on many other variables. If you think that our office can help you, feel free to give us a call at 717-766-5406 and schedule an appointment! I hope this article was informative! Like, share, and comment if you enjoyed this article!
Works Cited
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3. Chen C, Cavanaugh JM, Song Z, Takebayashi T, Kallakuri S, Wooley P. (2004.) Effects of nucleus pulposus on nerve root neural activity, mechanosensitivity, axonal morphology, and sodium channel expression. Spine. 29: 17-25.
4. Fazey PJ, Song S, Monsas S, Johansson L, Haukalid T, Price R, Singer K. (2006). An MRI investigation of intervertebral disc deformation in response to torsion. Clinical Biomechanics. 21 (5): 538-542.
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6. McHugh M, Johnson C, Morrison R. (2012). The role of neural tension in hamstring flexibility. Scandanavian Journal of Medicine and Science in Sports. 22: 432-435.
7. Olmarker K, Rydevik B, Holm S. (1989). Edema formation in spinal nerve roots induced by experimental, graded compression: an experimental study on the pig cauda equina with special reference to differences in effects between rapid and slow onset of compression. Spine. 14: 569-573.
8. Rade M, Pesonen J, Kononen M, Marttila J, Shacklock M, Vanninen R, Kankaanpaa M, Airaksinen O. (2017). Reduced spinal cord movement with the straight leg raise test in patients with lumbar intervertebral disc herniation. Spine. 42 (15): 1117-1124.
9. Takahashi K, Shima I, Porter R. (1999). Nerve root pressure in lumbar disc herniation. Spine. 24 (19): 2003-2006.