I have back pain. Chronic, annoying, sometimes debilitating back pain. I always figured it was from years of weight lifting and competitive martial arts. But my journey over the years through various diagnoses and treatments had me questioning the solely physical basis for any chronic pain. So what really causes our back pain?
Back pain affects around ¼ of people according to United States national surveys (Deyo, Mirza, & Martin, 2006) but the cause of back pain is still poorly understood. Within a mechanistic model we could make an a priori assumption that the causes are physical dysfunction or injury and this assumption also defines the diagnostic-to-treatment pathway for low back pain which commonly involves referals from a general practitioner to a physiotherapist to a back surgeon or specialist involving various tests along the way.
The challenge within this model of diagnosis and treatment is that there appears to be no firm causal link between the mere presence of spinal pathology (nor its absence) and back pain. A systematic review in Spine concluded that there is indeed no firm evidence for the presence or absence of a causal relationship between radiographic findings (such as disc space narrowing, osteophytes, sclerosis, spondylolysis and spondylolisthesis, spina bifida, transitional vertebrae, spondylosis, and Scheuermann's disease) and nonspecific low back pain (van Tulder, Assendelft, Koes, & Bouter, 1997). Further MRI discovery of bulges or protrusions may be coincidental due to the large amount of people without pain who exhibit the very same spinal anomalies (Jensen et al., 1994). In his 1992 paper in Current Orthopaedic Practice Dr Alf Nachemson states “Rarely are diagnoses scientifically valid, nor is the effectiveness of surgery proven by acceptable clinical trials.” (Nachemson, 1992)
Notwithstanding this intravertebral disk degeneration is a weak predictor of low-back pain in young adults (Salminen, Erkintalo , Laine, & Pentti, 1995), but this statistical correlation does not help the practitioner, nor patient to understand what is actually causing their back pain as there are large numbers of people who exhibit pain with pathology, and large numbers exhibiting pain without pathology.
It is well known that psychological variables (such as pain related to fear) worsen pain (Peters, Vlaeyen, & Weber, 2005). Cohort evidence suggests that low back pain disability is strongly predicted by psychosocial variables and the structural variables (as shown by MRI and discography testing) have only a weak association with back pain episodes and no association with disability or future medical care (Carragee, Alamin, Miller, & Carragee, 2005). A systematic review of prospective cohort studies featuring 20 publications concluded “Psychological factors (notably distress, depressive mood, and somatization) are implicated in the transition to chronic low back pain.” The authors go on to suggest that the development and testing of new clinical diagnostics and interventions taking into account these factors and that there is a need to clarify further the role of psychological factors, especially coping strategies and fear avoidance, in low back pain (Pincus, Burton, Vogel, & Field, 2002).
Serious pathology (such as a fracture) in which we would expect to see resultant back pain is exceedingly rare, accounting for less than 1% of cases of low back pain (Henschke et al., 2009).
Psychosocial factors may be beginning to be further elucidated, at least in a corrolary fashion by neuroimaging evidence suggesting that inappropriate cortical representation of proprioception may falsely signal incongruence between motor intention and movement, resulting in pain in a similar way that incongruence between vestibular and visual sensation may result in motion sickness (Harris, 1999). Others imply that chronic back pain is accompanied by brain atrophy and suggest that the pathophysiology of chronic pain includes thalamocortical processes (Apkarian et al., 2004).
A hypothesis suggested by some is that there is a ‘tension syndrome’ or compartment syndromes (Peck, Nicholls, Beard, & Allen, 1986) present that may help to explain the cause of idiopathic low back pain and that for which we believe (perhaps mistakenly) that there is a physical pathology, and that this may also have a psyco-emotional or psycho-social/psychospiritual basis.
This tension could be related to stress, or a self-limiting belief structure that is attempting to reduce further harm, potential injury or limiting a perceived threat activity, which indeed may or may not be dangerous at all.
There is clinical case series evidence suggesting that this indeed the case and that when people are aware of the reality that back pain may not be a physical dysfunction, but indeed may be simply a stress-tension or psychoneurophysiological inhibition that it may abate. There is scope within this to extend physical therapy into psychological or mind-body therapy modalities if this is indeed the case.
Apkarian, A. V., Sosa, Y., Sonty, S., Levy, R. M., Harden, R. N., Parrish, T. B., & Gitelman, D. R. (2004). Chronic Back Pain Is Associated with Decreased Prefrontal and Thalamic Gray Matter Density. The Journal of Neuroscience, 24(46), 10410-10415. doi: 10.1523/jneurosci.2541-04.2004
Carragee, E. J., Alamin, T. F., Miller, J. L., & Carragee, J. M. (2005). Discographic, MRI and psychosocial determinants of low back pain disability and remission: a prospective study in subjects with benign persistent back pain. The Spine Journal, 5(1), 24-35. doi: http://dx.doi.org/10.1016/j.spinee.2004.05.250
Deyo, R. A., Mirza, S. K., & Martin, B. I. (2006). Back Pain Prevalence and Visit Rates: Estimates From U.S. National Surveys, 2002. Spine, 31(23), 2724-2727 2710.1097/2701.brs.0000244618.0000206877.cd.
Harris, A. J. (1999). Cortical origin of pathological pain. The Lancet, 354(9188), 1464-1466. doi: http://dx.doi.org/10.1016/S0140-6736(99)05003-5
Henschke, N., Maher, C. G., Refshauge, K. M., Herbert, R. D., Cumming, R. G., Bleasel, J., . . . McAuley, J. H. (2009). Prevalence of and screening for serious spinal pathology in patients presenting to primary care settings with acute low back pain. Arthritis & Rheumatism, 60(10), 3072-3080. doi: 10.1002/art.24853
Nachemson, A. L. (1992). Newest Knowledge of Low Back Pain A Critical Look. Clinical Orthopaedics and Related Research, 279, 8-20.
Peck, D., Nicholls, P. J., Beard, C., & Allen, J. R. (1986). Are There Compartment Syndromes in Some Patients with Idiopathic Back Pain? Spine, 11(5), 468-475.
Peters, M. L., Vlaeyen, J. W. S., & Weber, W. E. J. (2005). The joint contribution of physical pathology, pain-related fear and catastrophizing to chronic back pain disability. Pain, 113(1–2), 45-50. doi: http://dx.doi.org/10.1016/j.pain.2004.09.033
Pincus, T., Burton, A. K., Vogel, S., & Field, A. P. (2002). A Systematic Review of Psychological Factors as Predictors of Chronicity/Disability in Prospective Cohorts of Low Back Pain. Spine, 27(5), E109-E120.
Salminen, J. J., Erkintalo , M., Laine, M., & Pentti, J. (1995). Low Back Pain in the Young A Prospective Three-Year Follow-up Study of Subjects With and Without Low Back Pain. Spine, 20(19), 2101-2107.
van Tulder, M. W., Assendelft, W. J., Koes, B. W., & Bouter, L. M. (1997). Spinal radiographic findings and nonspecific low back pain. A systematic review of observational studies. Spine (Phila Pa 1976), 22(4), 427-434.