Is Degenerative Disc Disease Painful?

‘Correlation doesn’t imply causation.’ It’s a commonly expressed caution in the health sciences. What it means is that things can tend to go together without necessarily causing each other. The classic example that statistic professors like to give is that air conditioner use is significantly correlated with street crime. Does the use of air conditioners cause street crime? No, of course, not and yet they do tend to go together. It’s actually only because they both tend to occur in the summer. When it’s hot outside, it’s true that people tend to use their air conditioners and it’s also true that people tend to loiter outside in the city, getting into trouble more often than in the cold winter months when people tend to stay indoors. With the example, we can see that just because things tend to go together they don’t also always cause each other.

What about things that hardly go together or things that don’t go together at all? Could we say that low levels of correlation or an altogether lack of correlation imply causation? On the face of it, it seems absurd to think that lack of correlation or even minimal correlation might imply causation. Who would think that A causes B when A and B have no relationship to one another or only a minimal association with one another? That inference, however, is exactly what we assume when we think that degenerative disc disease causes chronic back or neck pain.

The logic of correlational studies of degenerative disc disease and chronic spine pain

Degenerative disc disease is a common explanation for chronic back or neck pain. Degenerative disc disease is a general phrase that refers to a number of conditions or changes of the spine, such as loss of disc height, disc bulges, annular tears, disc herniations, endplate changes, neuroforaminal and spinal canal stenosis, among others. Healthcare providers typically identify their occurrence with either X-ray, CT or MRI scans. When these tests identify degenerative disc disease in the spine of someone experiencing chronic back or neck pain, many healthcare providers and their patients consider that the degenerative disc disease is the cause of the chronic pain. In other words, they believe that the degenerative disc disease is painful.

Healthcare providers and their patients commonly justify particular types of treatment with the notion that degenerative disc disease is causing chronic back or neck pain. Spine surgery and interventional pain procedures, in particular, but also certain types of physical therapy, all attempt to reduce pain by modifying specific types of degenerative changes of the spine. Again, the underlying justifying belief is that such degenerative changes of the spine are painful.

How valid is this justification? In other words, how true is it that degenerative disc disease causes chronic back or neck pain?

The question is actually tricky to answer, especially if we want to show that it is in fact true. Theoretically, the best way to answer it would be to run a true experiment, where we induce various degenerative changes to the spine in a number of people and see whether they have pain in the back or neck (wherever the degenerative change was induced). However, we don’t know how to make degenerative changes to the spine, at least not exactly as they occur naturally. Additionally, even if we did know how, there would be all sorts of ethical problems in producing degenerative disc disease in human subjects. For instance, we don’t know how to reverse it and so we’d be inducing permanent damage to people. Because of these challenges, we don’t tend to perform true experiments when looking at the relationship between degenerative disc disease and chronic neck and back pain.

Instead, we generally rely on a different form of research in the scientific study of chronic pain – correlational research. In correlational research, we measure certain variables, such as the occurrence of degenerative disc disease and back or neck pain, and see whether they tend to go together. If two things, such as degenerative disc disease and pain, are highly correlated (i.e., they tend to go together almost always), we can at least say that one may cause the other. As we discussed in the introduction of this piece, though, we cannot say with confidence that there is a causal relationship when two things are highly correlated. There may be other factors that cause the two to occur together all the time (i.e., think of the air conditioner use and street crime example). Nonetheless, it is helpful to see whether they correlate together and what the strength of the correlation is. The reason is that if they don’t correlate at all or if the correlation is very weak, then we can say with confidence that they don’t cause each other.

To understand, we need to look at the following reasoning: when one thing causes another thing, they must occur together in some demonstrable way; if, however, when one thing occurs, another thing may or may not occur, they have no relationship to each other and so we cannot say that there is a causal relationship. A causal relationship presupposes a correlational relationship. Now, as we have said before, a correlational relationship is not enough to demonstrate a causal relationship, but to have a causal relationship, there at least has to be a correlational relationship. We have to at least be in the right ballpark, as it were. Without a correlational relationship, though, we can say with much greater confidence that we are not even in the right (i.e., causal) ballpark. In other words, if we find no correlation, we can safely assert that there is no causal relationship.

A similar, albeit slightly different logic holds with weak correlations – the situation in which two things go together in some minimal ways. With such correlations, we can say that there may be a causal relationship between the variables, just as we said with strong correlations, but we can’t know for sure because correlation doesn’t imply causation. Now, with weak correlations, however, we can go a step further. We can assume that even if there was a causal relationship between the two variables, we know that there has to be more to the picture than simply the two weakly correlated variables. In other words, there has to be additional causal variables coming into play, because if there weren’t the correlation would have to be strong. The weak correlation, even in cases where we might assume a causal relationship, shows that the variable is only part of the cause – and only a small part at that.

It would be helpful to take an example. Let’s suppose that we did a study of the relationship between the presence of eating utensils and cookware in the kitchen on the one hand and how much food people ate on the other hand. In a sample of 1,000 people, we measured a) the extent to which they had eating utensils and cookware in the kitchen and b) how much they ate on average over the course of a month. Let’s further suppose we found a weak, statistically significant, relationship between our two variables of interest. It’s a fantastical example, of course, but we might see how it could be true: the presence of eating utensils and cookware could play some small role in how much you ate on average – if you don’t have a way to prepare and eat food, it could affect how much you eat. However, we can also immediately see that there’s more to the picture in terms of what goes into the fact of how much food people eat. The extent to which you have ways to prepare and eat food are not the only variables that can lead to eating. People can eat raw foods; they can eat with their hands; they can buy prepared foods in the grocery store, delis, and fast food restaurants; they can go out to eat in sit-down restaurants; and so on. Personal characteristics of the people can also play a role: how hungry they are or how much stress they are under or how busy they are can also affect how much people eat – even in people who don’t have adequate means to prepare food. In all these ways, we can see that a weak, statistically significant, correlational relationship cannot explain the whole nature of the relationship between two variables, even when we assume that they are in some ways causally related.

As we will see in the following review of the correlational research on degenerative disc disease and chronic back or neck pain, degenerative changes of the spine fit into one of these two categories: they either have no relationship at all with chronic back or neck pain, or they are only weakly related to chronic back or neck pain. As such, we can conclude with confidence one of two things, depending on the type of degenerative disc disease we are discussing. First, in the case where research repetitively shows no correlational relationship between certain types of degenerative disc disease and chronic back or neck pain, these particular types of degenerative changes do not cause pain, despite the common belief that they do. Second, in the case where research repetitively shows a weak, statistically significant, correlational relationship between certain types of degenerative disc disease and chronic back or neck pain, these particular types of degenerative disc disease may play some role in producing pain, but we know that it is only a minimal role, even if we assume that the correlation reflects a causal relationship. In other words, the weak correlation between certain types of degenerative disc disease and pain shows that the lion’s share of what’s causing the pain is something else entirely. This statement too stands in stark contrast to the common belief that degenerative disc disease is the predominant cause of chronic back or neck pain.

Let’s, then, review the correlational research on the relationship between the different types of degenerative disc disease and chronic back or neck pain.

Correlation (or lack thereof) between pain and degenerative disc disease

In a review of early studies, van Tulder, at al., (1997) found weak significant associations between back pain and disc space narrowing, osteophytes, and sclerosis, with odds ratios in the range of 1.2-3.3. Other degenerative changes, such as spondylosis, spondyolisthesis, and kyphosis had no relationship to back pain.

In their review of the literature on the natural history and clinical significance of disc herniation, Grande, Maus, and Carrino (2012) conclude that there is no relationship between any characteristics of disc herniation, including size or severity, and subsequent symptoms of patients.

Mitra, Cassar-Pullicino and McCall (2004) found no relationship between evidence of an annular tear in the disc and pain.

Jarvinen, et al., (2015) found no significant correlation between Modic 1 or Modic 2 changes and low back pain.

de Schepper, et al., (2010) studied the relationship between osteophytes, disc space narrowing, and low back pain. They found that disc space narrowing, especially, at more than one level, was most significantly related to low back pain, but only weakly, with an odds ratio of 2.4.

In a more statistically oriented review, Chou, et al, (2011), systematically searched the literature and combined studies to determine the odds ratio for having lumbar degenerative changes and chronic low back pain. They found a significant, yet weak, association between the two. The range for the odds ratio was between 1.8-2.8.

Livshits, et al., (2011) found a significant relationship between all degenerative changes of the spine and pain with an odds ratio of 3.2.

In a study published after the Chou, et al. findings, Nemoto, et al., (2012) found a significant correlation between vertebral osteophytes and low back pain, but the odds ratio was a little greater at 3. In contrast to the de Schepper, et al, study cited above, they found no correlation between disc space narrowing and back pain.

All these data are what likely led Bogduk (2012), one of the founding fathers of interventional pain management, to conclude, “Degenerative changes [of the spine] lack any significant correlation with spinal pain.”

These findings are also similar to the relationship between degenerative disc disease and pain related disability. Quack, et al., (2007) found either no relationship or only weak correlations between lumbar degenerative changes and mobility. Sirvanci, et al., (2008), found no significant relationship between lumbar spinal stenosis and perceived disability, as measured by the Oswestry Disability Index. Lohman, et al., (2006) found no relationship between spinal stenosis and pain or scores on the Oswestry Disability Index. Remes, et al., (2005) in a cohort of patients who underwent fusion for spondylolisthesis twenty years ago, found no relationship between lumbar degenerative changes and the same measure of disability. Similarly, looking at a number of biological and lifestyle factors, Wilkens, et al., (2013) found that degenerative changes as found on imaging failed to correlate with perceived disability one year later as measured by the Roland-Morris Disability Questionnaire.

Conclusion

This review of the literature shows that the various types of degenerative disc disease either have no relationship to pain and disability or only a weak correlation to pain and disability. What this means is that degenerative disc disease is likely not painful. At best, it plays a minimal role in the cause of chronic back or neck pain. The true cause of chronic back or neck pain must be something else entirely.

For more information on degenerative disc disease, please see the previous blog post and the Institute for Chronic Pain content page on degenerative disc disease.

References

Bogduk, N. (2012). Degenerative joint disease of the spine. Radiology Clinics of North America, 50(4), 613-628. doi: 10.1016/j.rcl.2012.04.012

Chou, D., Semartzis, D., Bellabarba, C., Patel, A., Luk, K., Kisser, J. M., & Skelly, A. C. (2011). Degenerative magnetic resonance imaging changes in patients with chronic low back pain: A systematic review. Spine, 36, S43-S53. doi: 10.1097/BRS.0b013e31822ef700

Del Grande, F., Maus, T. P., & Carrino, J. A. (2012). Imaging the intervetebral disk: Age-related changes, herniation, and radicular pain. Radiology Clinics of North America, 50(4), 629-649. doi: 10.1016/j.rcl.2012.04.012

de Schepper, E., Damen, J., van Meurs, J. B., Ginai, A. Z., Popham, M., Hofman, A., Koes, B. W., & Bierma-Zeinstra, S. M. (2010). The association between lumbar disc degeneration and low back pain: The influence of age, gender, and individual radiographic features. Spine, 25(5), 531-536. doi: 10.1097/BRS.0b013e3181aa5b33

Jarvinen, J., Karppinen, J., Niinimaki, J., Haapea, M., Gronblad, M., Luoma, K., & Rinne, E. (2015). Associations between changes in lumbar Modic changes and low back symptoms over a two year period. BMC Musculoskeletal Disorder, 16, 98. doi: 10.1186/s12891-015-0540-3

Livshits, G., Popham, M., Malkin I., Sambrook, P. M., MacGregor, A. J., Spector, T., & Williams, F. M. (2011). Lumbar disc degeneration and genetic risk factors are the main risk factors for low back pain in women: The UK twin spine study. Annals of Rheumatic Disease, 70(10), 1740-1745. doi: 10.1136/ard.2010.137186

Lohman, C. M., Tallroth, K., Kettunen, J. A., & Lindgren, K. (2006). Comparison of radiologic signs and clinic symptoms of spinal stenosis. Spine, 31(16), 1834-1840.

Maus, T. (2010). Imaging the back pain patient. Archives of Physical Medicine and Rehabilitation, 21(4), 725-766. doi: 10.1016/j.pmr.2010.07.004

Mitra, D., Cassar-Pullicino, V. N., & McCall, I. W. (2004). Longitudinal study of high intensity zones on MR of lumbar intervetebral discs. Clinical Radiology, 59(11), 1002-1008.

Nemoto, O., Kitada, A., Naitou, S., Tsuda, Y., Matsukawa, K., & Ukegawa, Y. (2012). A longitudinal study for incidence of low back pain and radiological changes of lumbar spine in asymptomatic Japanese military young adults. European Spine Journal, 22, 453-458. doi: 10.1007/s00586-012-2488-4

Quack, C., Schenk, P., Laeubil, T., Spillmann, S., Hodler, J., Michel, B. A., & Klipstein, A. (2007). Do MRI findings correlate with mobility tests? AN explorative analysis of the test validity with regard to structure. European Spine Journal, 16(6), 803-812.

Remes, V. M., Lamberg, T. S., Tervahartiala, P. O., Helenius, I. J., Osterman, K., Schlenzka, D., Yrjonen, T., Seitsalo, S., & Poussa, M. S. (2005). No correlation patient outcome and MRI findings 21 years after posterior or posterolateral fusion for isthmic spondylolisthesis in children and adolescents. European Spine Journal, 14(9), 833-842.

Sirvanci, M., Bhatia, M., Ganiyusufoglu, K. A., Duran, C., Tezer, M., Ozturk, C., Aydogan, M., & Hamzaoglu, A. (2008). Degenerative lumbar spinal stenosis: Correlation with Oswestry Disability Index and MR imaging. European Spine Journal, 17(5), 679-685. doi: 10.1007/s00586-008-0646-5

van Tulder, M. W., Assendelft, W. J., Koes, B. W., & Bouter, L. M. (1997). Spine, 22(4), 427-434.

Wilkens, P., Scheel, I. B., Grundes, O., Hellum, C., & Storheim, K. (2013). Prognostic factors of prolonged disability in patients with chronic low back pain and lumbar degeneration in primary care: A cohort study. Spine, 38(1), 65-74. doi: 10.1097/BRS.0b013e318263bb7b

Author: Murray J. McAllister, PsyD

Date of last modification: 5-31-2015

Is Degenerative Disc Disease Inevitably Degenerative?

It’s common to be upset when you’ve been told that you have degenerative disc disease. It’s an awful sounding diagnosis. It sounds like you have a disease that is deteriorating your spine. And on top of it all, it doesn’t sound like there’s much you can do about it. The spine, it seems, is inevitably degenerating.

Patients commonly express the belief that their chronic back or neck pain is a progressive condition that will unavoidably lead to greater and greater pain and disability. They’ve been told that they have degenerative disc disease and that it is the cause of their pain. It was found on their MRI scan of the spine. Since the cause of their pain is called ‘degenerative,’ they understandably believe that it’s inevitable that they are going to get worse. Their future, it seems, holds nothing but increasing pain and impairment.

Sometimes, healthcare providers believe that degenerative disc disease is inevitably degenerative too. Commonly, patients tell me that they’ve been told by their healthcare provider that they will end up in a wheelchair someday or that the provider is surprised the patient can walk upright given the extent of the findings of degenerative disc disease that’s evident on the MRI scan. Such comments by healthcare providers seem to indicate that they too believe that degenerative disc disease is inevitably degenerative, progressively leading to a worsening of pain and disability.

What is the natural course of degenerative disc disease?

How confident should we be in this belief that degenerative disc disease is inevitably degenerative? What does science tell us about what happens to so-called degenerative changes of the spine over time? In healthcare, studies of what happens to health conditions over time when left untreated are called ‘natural history’ studies. Such studies simply track a condition over time to see what its natural trajectory is– whether the condition tends to get better or worse. It would be helpful to look at natural history studies of the conditions that fall under the category of degenerative disc disease. We’d then know what the natural trajectory is for such conditions.

Degenerative disc disease is a catchall phrase for a number of conditions of the spine. These conditions are typically evident on CT and MRI scans. They are a loss of disc height, disc bulges and herniations, annular tears, endplate changes, osteophyte complexes, neuroforaminal stenosis, and central canal stenosis, among others.

Let’s look at what happens to these conditions over time. Many chronic back or neck pain patients have such degenerative changes in their spine as evidenced by MRI or CT scans and it will be helpful to know something about what typically happens to them if you have them. Contrary to popular belief, we will find that the changes to the spine that we call degenerative disc disease are not inevitably degenerative.

When I review this research with patients, they are a little surprised. They have long thought of their condition as inevitably progressive and it can take a little bit of time to get used to the idea that their condition is not as degenerative as they had thought it to be. Moreover, they are frequently a little skeptical. One of the most common exceptions to the review of this research goes something like, ‘Well, Doc, I’ve been told that my degenerative disc disease is very severe… Severe or advanced degenerative disc disease is going to get worse. How could it not?’ That is to say, a common belief about degenerative disc disease is not only that it is inevitably degenerative, but that the more advanced it is the more progressive it will be. Another way to put it is the belief that the worst or most advanced stages of degenerative disc disease will always tend to lead to the most severe pain and disability. So, let’s review what science tells us about what happens to the most advanced or worst degenerative changes over time too.

Specifically, with our review of natural history studies of degenerative disc disease, we want to determine the answers to two questions:

  • Do degenerative changes to the spine inevitably worsen?
  • What happens to the most severe degenerative changes?

 Natural history studies of degenerative disc disease

Symmons, et al., (1991) were some of the first investigators to look at these questions. They took X-rays of 742 women aged 45 or older and then repeated the X-rays 8 to 11 years later. They broke women into two groups, those with back pain and those without back pain. They found degenerative changes in both groups. They also found that degenerative disc disease progressed most often in those with back pain. Over the study period, they found that almost 60% of women with back pain had a progression of their degenerative disc disease; whereas, a little more than 30% of women without back pain had a progression of their degenerative disc disease. Notice, however, that progression of degenerative disc disease is not inevitable. The remaining 40% of those with back pain had degenerative disc disease that did not get worse. The remaining 70% of the women without back pain had degenerative disc disease that did not get worse.

This study relied on X-rays, rather than more accurate CT or MRI scans. Is there evidence of the same findings with CT or MRI scans?

Using MRI scans on a repeated basis, Matsubara, et al., (1995) followed 32 patients with herniated discs in their lumbar spine over the course of a year. They found that 62% of the disc herniations spontaneously reduced in size and the remaining 38% of herniations did not get worse. In this study, we see a significant degenerative disc problem – herniations – tending to get better the majority of the time. Even when disc herniations failed to get better, they did not tend to get worse. Here, we find that the disc herniations are not inevitably degenerative.

These researchers also found data that pertains to the severity of disc herniations. Contrary to the popular belief that the worst problems tend to become more problematic, they found that the larger the disc herniation, the more it reduced.

Another spinal condition that falls under the category of degenerative disc disease are endplate changes. Hutton, et al., (2011) reviewed two groups of patients with lumbar-related endplate changes who had had MRI’s repeated over time. The first group was 36 patients with a minimal level of endplate changes. The second group was 22 patients with a more advanced stage of such changes. Of the first group with less significant endplate changes, half remained the same; a little less than half got worse; and two patients reversed back to normal. Of the second group with the more advanced changes, most remained the same; some got better and none got worse.

Here again, we see two important facts about this specific type of degenerative change. First, in its least advanced stage, sometime it does get worse, but only less than half the time. Thus, we really can’t say it is inevitable that it gets worse. Second, contrary to the notion that the more severe spine problems always lead to more severe consequences, we see that the advanced stages of endplate changes generally stay the same. Sometimes it gets better, but they don’t tend to get worse.

Park, et al., (2013) found in a sample of 27 cervical spondylolisthesis patients that only three had a progressive worsening of their condition over a 2-7 year follow-up period. None of the three experienced any significant neurological injury or an increase in their symptoms as a result.

Humphreys, et al., (1998) looked at still other conditions of the spine, which are associated with degenerative disc disease. They found that foraminal stenosis did in fact narrow with age but found no progression of disc height, lordosis, or central canal stenosis. So, here again, we find that degenerative changes of the spine are far from inevitably degenerative.

Regarding the latter, Karadimas, et al., (2013) reviewed the literature on cervical spondyltic myelopathy, or a degenerative narrowing of the spinal cord in the area of the neck, and found that the condition naturally worsened in 20-60% of the cases. Again, we see a significant degenerative condition can get worse, but does not always get worse. Indeed, depending on the study, 40-80% of the time it does not get worse.

Some might counter with a subtle variation of the second question we have been attempting to review, namely that the most advanced degenerative disc disease tends to be more degenerative. They might acknowledge that degenerative disc disease itself may not inevitably become worse. They might even acknowledge that the most advanced stages of such changes don’t tend to inevitably get worse. However, they might argue that the most severe degenerative changes to the spine do in fact lead to greater pain and/or a greater decline in functioning. In other words, those with the most severe degenerative disc disease will inevitably experience the greatest pain and disability.

A recent study by Berg, et al., (2013) inadvertently sheds light on this point. They were interested in looking at whether degenerative disc disease correlates with pain and disability in a sample of 170 low back pain patients who had been recommended for disc replacement surgery at either of the two lowest disc levels of the lumbar spine (i.e., L4-5 & L5-S1). Presumably, the degenerative disc disease evident at these two levels was severe enough to have the surgery recommended to them. Interestingly, they found no significant correlation at all between degenerative disc disease and either pain or disability. Even among a subgroup of people with the most severe degenerative changes (the severest of the severe), they still found no correlation. They subsequently added findings of facet arthropathy, another degenerative condition, and with the combination of degenerative disc and facet changes they still found no correlation between such changes and either pain or disability. In other words, neither more severe findings of degenerative disc disease nor a greater amount of such degenerative conditions lead to a worsening of pain or impairment. (This study highlights another interesting question to which we tend to all assume we know the answer – to what extent does degenerative disc disease explain chronic back or neck pain. This question will be taken up in our next blog post).

Concluding remarks

To summarize, we set out to determine the truth of certain common beliefs that patients have about degenerative disc disease. These beliefs are that degenerative disc disease is inevitably going to worsen, or at the very least the most severe degenerative changes are always going to get worse. By reviewing what the science tells us about degenerative disc disease, we see that neither of these beliefs are true. While degenerative changes do sometimes get worse, they very often either remain the same or get better. Also, we see evidence that the worse the degenerative condition is, the more it tends to either stay the same or get better.

Has your healthcare provider ever told you or implied that degenerative disc disease was inevitably going to get worse? Why do you think that this belief continues to be common when the scientific literature doesn’t support it?

References

Berg, L., Hellum, C., Gjertsen, O., Neckelmann, G., Johnsen, L. G., Storheim, K., Brox, J. I., Eide, G. E., & Espeland, A. (2013). Do more MRI findings imply worse disability or more intense low back pain? A cross-sectional study of candidates for lumbar disc prosthesis. Skeletal Radiology, 42(11), 1593-1602.

Humphreys, S. C., Hodges, S. D., Patwardhan, A., Eck, J. C., Covington, L. A., & Sartori, M. (1998). The natural history of the cervical foramen in symptomatic and asymptomatic individuals aged 20-60 years as measured by magnetic resonance imaging: A descriptive approach. Spine, 23, 2180-2184.

Hutton, M. J., Baker, J. H., & Powell, J. M. (2011). Modic vertebral body changes: The natural history as assessed by consecutive magnetic resonance imaging. Spine, 36, 2304-2307.

Karadimas, S. K., Erwin, W. M., Ely, C. G., Dettori, J. R., & Fehlings, M. G. (2013). Pathophysiology and natural history of cervical spondyltic myelopathy. Spine, 38(22S), S21-S36. doi: 10.1097/BRS.0b013e318a7f2c3

Matsubara, Y., Kato, F., Mimatsu, K., Kajino, G., Nakamura, S., & Nitta, H. (1995). Serial changes on MRI in lumbar disc herniations treated conservatively. Neuroradiology, 37, 378-383.

Park, M. S., Moon, S. H. Lee. H. M., Kim, S. W., Kim, T. H., Suh, B. K., & Riew, K. D. (2013). The natural history of degenerative spondylolisthesis of the cervical spine with 2-7year follow-up. Spine, 38(4), E205-E210. doi: 10.1097/BRS.0b013e1827de4fd

Symmons, D. P., van Hemert, A. M., Vandenbroucke, J. P., & Valkenburg, H. A. (1991). A longitudinal study of back pain and radiological changes in the lumbar spines of middle aged women. II. Radiographic findings. Annals of the Rheumatic Diseases, 50, 162-166.

Author: Murray J. McAllister, PsyD

Date of last modification: 3-10-2014