Factors Associated with Functional Disability and Walking Capacity in Adults with Chronic Low Back Pain: A Cross-Sectional Study

Background/Objectives: Disability in chronic low back pain (CLBP) is multifactorial, yet the independent associations of pain, fear-avoidance beliefs, and comorbidity burden with self-reported disability and performance-based walking capacity remain unclear, particularly in Saudi Arabia. This study examined factors independently associated with functional disability and walking capacity in adults with CLBP and explored whether disability was independently associated with walking capacity after accounting for demographic and clinical factors. Methods: This cross-sectional study included 339 adults with CLBP. Functional disability was assessed using the Oswestry Disability Index (ODI), walking capacity using the 6-Minute Walk Test (6MWT), and fear-avoidance beliefs using the physical activity (FABQ-PA) and work (FABQ-Work) subscales of the Fear-Avoidance Beliefs Questionnaire. Comorbidity burden was quantified as an unweighted count of previously diagnosed chronic conditions reported by participants and BMI-defined obesity. Multiple linear regression was used to examine factors independently associated with disability and walking capacity. The disability model included age, sex, pain intensity, FABQ-PA, FABQ-Work, and comorbidity burden. Walking capacity was examined using two models: the first included the same factors, whereas the second exploratory model additionally included ODI to examine whether disability was independently associated with 6MWT distance. Results: Bivariate analyses showed that pain intensity was positively correlated with FABQ-PA and FABQ-Work (r = 0.303–0.355), while ODI was positively correlated with comorbidity burden (r = 0.170). The 6MWT was negatively correlated with pain intensity, FABQ-PA, and FABQ-Work (r = −0.162 to −0.170) and more strongly with ODI (r = −0.550). In the adjusted disability model, comorbidity burden was the only factor independently associated with ODI score, with each additional comorbid condition associated with a 2.30-point higher ODI score (B = 2.296, 95% CI 0.834 to 3.759, p = 0.002). In the first adjusted walking-capacity model, higher pain intensity was independently associated with shorter 6MWT distance (B = −5.108, 95% CI −10.05 to −0.17, p = 0.044), while the other factors were not significantly associated with walking capacity. In the second adjusted walking-capacity model, greater disability was independently associated with shorter 6MWT distance (B = −3.996, 95% CI −4.655 to −3.337, p < 0.001). None of the other factors remained significantly associated with walking capacity in this model. Conclusions: Greater comorbidity burden was independently associated with greater disability in adults with CLBP, while greater disability was strongly associated with poorer walking capacity, highlighting the relevance of comorbidity burden and disability to functional limitations in CLBP.