Re-examining the Disc-Centric Interpretation of Chronic Low Back Pain: A Narrative Review

Chronic low back pain (CLBP) is among the leading causes of global disability. Magnetic resonance imaging (MRI) of the lumbar spine commonly demonstrates degenerated intervertebral discs and/or disc bulging that is regarded as the key contributor to the development of pain. However, degenerative changes of the disc are prevalent in asymptomatic people, thereby calling into question the specificity of these findings. In addition, the assessment and management of CLBP are currently based predominantly on the concept of the disc as the main source of pain and associated disability. The current narrative review aims to question an exclusive focus on disc pathology and to explore the potential contribution of paraspinal muscle dysfunction and biomechanical factors in CLBP. An electronic literature search of PubMed, Scopus, and Web of Science databases was performed for the relevant English-language articles published between January 1990 and February 2025. Studies were chosen according to established eligibility criteria, which encompassed relevance to CLBP in adults, emphasis on paraspinal muscle morphology, spinal biomechanics, or lumbar disc imaging, and the provision of clinically or biomechanically interpretable results. A narrative synthesis of results was conducted, while no quantitative analysis was performed. MRI of asymptomatic patients commonly shows degenerated intervertebral discs and disc bulging, with no consistent relationship between the presence of degenerative changes and pain intensity. Conversely, changes in the muscles, especially lumbar multifidus muscle atrophy, fatty infiltration, and asymmetry, seem to consistently correlate with the presence of CLBP and functional impairment. The longitudinal data suggest the persistence of muscle dysfunction after the remission of pain episodes in CLBP patients. Further, studies on the biomechanics of the spine showed the impact of muscle dysfunction on spinal load distribution and intradiscal pressure (the internal pressure within the intervertebral disc that reflects load transmission through the spine), suggesting that disc bulging may, in some cases, represent a biomechanical adaptation. Degenerative findings are non-specific and should be interpreted considering functional and biomechanical factors. Greater consideration of muscular and biomechanical factors may complement imaging findings in the assessment and management of CLBP. Given the narrative design and predominance of observational evidence, the findings of this review should be interpreted as hypothesis-generating and should not be considered definitive evidence of causal relationships.