Longitudinal associations of kinematics and fear-avoidance beliefs with disability, work ability and pain intensity in persons with low back pain

Background: Impaired lumbar movement has cross-sectionally been associated with low back pain (LBP); however, the consequence of impaired movement on disability and pain in persons with LBP is poorly understood. Furthermore, fear-avoidance beliefs (FAB) may influence spinal movement, but the relation between fear-avoidance and kinematics is unclear. Objectives: To investigate the longitudinal associations of kinematics and FAB with disability, work ability and pain in patients with LBP. Further, to explore associations between FAB and kinematics. Design: Prospective observational study. Method: Kinematic measures were performed on 44 persons with LBP at baseline, three and nine months. Motion sensors identified range-of-motion and velocity during a spinal flexion/extension. FAB, disability, work ability and pain were reported at all time points using questionnaires. Results: Increased range-of-motion was weakly associated with less disability (-0.14 points, 95% CI -0.22 to -0.06). Velocity was not associated with disability, work ability or pain. Higher FAB of physical activity were associated with more disability (1.50 points, 95% CI 0.51 to 2.49) and pain (0.37 points, 95% CI 0.11 to 0.62). Higher work-related FAB was associated with lower work ability (- 0.37 points, 95% CI -0.68 to - 0.05). Moreover, higher FAB showed weak associations with lower velocity in the initial movement phase (- 3.3 degrees/s, 95% CI -6.1 to - 0.5). Conclusions: Of the kinematic measures, only range-of-motion was related to disability. Higher FAB was weakly associated with all self-reported outcomes and with lower velocity only at the initial flexion phase. However, the magnitude of these associations suggest marginal clinical importance.