Functional Resilience in Chronic Low Back Pain: Dissociating Magnetic Resonance Imaging Abnormalities From Real-World Disability in the Wakayama Spine Study.

Objective: Low back pain (LBP) is common, yet many individuals maintain normal activities of daily living despite chronic symptoms and structural changes evident on imaging. We hypothesized that functional resilience, defined as preserved functional capacity despite pain and age‑typical degenerative changes, represents a meaningful clinical phenotype, and that function‑centered outcome measures would better discriminate disability status than structural imaging features. Methods: This study analyzed 347 participants reporting LBP from the Wakayama Spine Study (N=866). Maintained function was defined a priori as Oswestry Disability Index (ODI) ≤20%. We compared those with maintained function (n=220, 63.4%) to those with impairment (n=127) across demographics, lifestyle, metabolic components, physical performance (grip strength, gait speed), and lumbar magnetic resonance imaging (MRI) findings. Multivariable logistic regression among participants with LBP, including age, sex, obesity, metabolic factors, pain intensity, physical performance, and MRI phenotypes, was used to identify independent predictors of functional resilience. Results: Functional resilience was common: 63.0% of LBP participants had ODI ≤20%. Resilient individuals were younger (65.0±11.9 years vs. 74.6±10.9 years, p<0.001) with superior physical performance. In multivariable models, male sex predicted maintained function (odds ratio [OR], 1.76; 95% confidence interval [CI], 1.03-3.00; p<0.05), while obesity (body mass index ≥25 kg/m2) was associated with reduced odds of resilience (OR, 0.50; 95% CI, 0.30-0.84; p<0.01). Standard MRI features, including disc degeneration, Modic changes, and Schmorl nodes, were not independently associated with functional status after adjustment, despite disc degeneration being highly prevalent even among resilient participants (95.4%). Conclusion: These data confirm that functional resilience is common in LBP and is not negated by the presence of structural MRI abnormalities. Among LBP patients, male sex and absence of obesity are independent predictors of maintained function, whereas standard MRI features do not independently predict functional status after age adjustment. Function-centered metrics (ODI, gait speed, grip strength) better discriminate functional status than structural imaging findings.