In low back pain there are clear clinical differences seen between recurrent and chronic low back pain patients. According to the definition, recurrent low back pain patients suffer from pain flares of at least 24 hours, followed by a pain free episode of at least 1 month (de Vet et al, 2002). Chronic low back pain patients however, are characterized by sustained low back pain for at least 3 months (Andersson, 1999). Furthermore, even within the population of chronic low back pain a large heterogeneity exists. Despite the clinical differences between subgroups of low back pain, clinical practices frequently treat them as one and the same.
Besides differences in clinical presentation, there are also differences in muscle characteristics established between recurrent and chronic low back pain patients. Several decades ago, research observed smaller muscles, accompanied by enhanced fat infiltration in chronic low back pain patients compared to recurrent low back pain patients (Hultman et al, 1993). Furthermore, when subdividing chronic low back pain into subgroups with (1) continuous chronic low back pain patients, having pain every day and (2) non-continuous chronic low back pain patients, characterized by 3 to 4 pain days a week (and 3 to 4 pain free days a week) and recurrent low back pain these differences are also seen in muscle structural characteristics in the lumbar muscles. With an enhanced fat infiltration in continuous chronic low back pain patients compared to recurrent and non-continuous chronic low back pain patients (Goubert et al, 2017).
Alterations in lumbar muscle structure influences lumbar muscle function. And indeed, continuous chronic low back pain patients are characterized by less efficient lumbar muscle activity work compared to recurrent low back pain patients. It is assumed that in the population of patients with continuous chronic low back pain the large amount of fat infiltration in the muscles hamper proper muscle function. However, the population of patients with non-continuous chronic low back pain are also characterized by less efficient lumbar muscle work. Since no enhanced fat infiltration is seen in this group, other explanations are urged here. Possibly, other structural alterations, such as changes in fiber type distribution are involved in the degeneration of muscle function in the lumbar muscles of non-continuous chronic low back pain patients (Goubert et al, 2017). These findings highlight the importance of addressing both muscle structure and muscle function in the treatment approaches of continuous chronic low back pain. In non-continuous chronic low back pain patients muscle function needs attention during treatment.
Recently, the research focus in chronic pain has shifted from musculoskeletal dysfunctions to alterations in pain processing. It is hypothesised that complaints in the chronic low back pain population are dominantly determined by alterations in pain mechanisms. Some studies have demonstrated alterations in pain processing in chronic low back pain, but results remain inconsistent (O'Niell et al, 2007, Roussel et al, 2013, Goubert et al, 2017). It is therefore opposed that only a subgroup of chronic low back pain patients is characterized by alterations in pain processing. For instance, recurrent low back pain patients seem to be characterized by a normal pain processing (Goubert et al, 2017). However, in the subgroup of chronic low back pain patients whereby there is an alteration in pain processing, it is advised to focus on the alterations in pain mechanisms instead of muscle function during treatment, prior and in addition to graded functional activity reconstruction (Malfliet et al, 2017).
Psychosocial aspects play a key role in the recurrence and/or chronicity of low back pain complaints. Early detection of psychological pitfalls such as fear of movement, pain catastrophizing, anxiety and depression are essential to guide the treatment approaches in these patients. Recent research in differences between recurrent, non-continuous chronic and continuous chronic low back pain patients revealed that non-continuous chronic low back pain patients, characterized by pain flares as well as pain free episodes a week, are characterized by a less favourable psychological mind set (Goubert, 2017, unpublished data). A theory would be that being frequently confronted with short periods of being pain free makes it harder to accept pain flares, whereas patients with continuous chronic pain flares, resign themselves to the current situation.
In summary, patients with recurrent low back pain differ from patients with chronic low back pain on several levels. These findings can help clinicians to direct their treatment approaches for the different groups of low back pain in the light of individual differences.
Dorien Goubert is a postdoctoral researcher at the University of Ghent, Belgium, and is a member of the Pain in Motion research group. She worked as a physiotherapist and manual therapist in clinical practice for several years before engaging in research. She obtained her PhD in the field of low back pain, researching the differences between recurrent and chronic low back pain.
2017 Pain in Motion
References and further reading:
de Vet HCW, Heymans MW, Dunn KM, et al. Episodes of low back pain: a proposal for uniform definitions to be used in research. Spine (Phila Pa 1976). 2002;27(21):2409-2416.
Andersson GB. Epidemiological features of chronic low-back pain. Lancet. 1999;354(9178):581-585.
Hultman G, Nordin M, Saraste H, Ohlsèn H. Body composition, endurance, strength, cross-sectional area, and density of MM erector spinae in men with and without low back pain. J Spinal Disord. 1993;6(2):114-123. https://www.ncbi.nlm.nih.gov/pubmed/8504222
Goubert, De Pauw R, Meeus M, Willems T, Cagnie B, Schouppe S, Van Oosterwijck J, Dhondt E D. Lumbar muscle structure and function in chronic versus recurrent low back pain: a cross-sectional study. Clin J painSpine J. 2017 Sep;17(9):1285-1296.
O’Neill S, Manniche C, Graven-Nielsen T, Arendt-Nielsen L. Generalized deep-tissue hyperalgesia in patients with chronic low-back pain. Eur J Pain. 2007;11(4):415-420.
Roussel N a, Nijs J, Meeus M, Mylius V, Fayt C, Oostendorp R. Central sensitization and altered central pain processing in chronic low back pain: fact or myth? Clin J Pain. 2013;29(7):625-638. https://www.ncbi.nlm.nih.gov/pubmed/23739534
Goubert, D, Danneels, L, Graven-Nielsen T, Descheemaeker F, Coppieters I, Meeus M. Differences in pain processing between patients with chronic low back pain, recurrent low back pain and fibromyalgia. Pain Physician. 2017 May;20(4):307-318.
Malfliet A, Kregel J, Meeus M, Cagnie B, Roussel N, Dolphens M, Danneels L NJ. Applying contemporary neuroscience in exercise interventions for chronic spinal pain: treatment protocol. Brazilian J Phys Ther. 2017 Sep-Oct; 21(5): 378–387.
Dorien G. Differences in psychosociale factors between recurrent low back pain, non-continuous chronic low back pain and continuous chronic low back pain. Unpubl data.