Lumbopelvic rhythm analysis by quartiles: Identification of differences in lumbar and pelvic contribution during trunk flexion and extension in subjects with low back pain of different origin. A case-control study.

Low back pain (LBP) can alters spinal kinematics. However, for adequate clinical care, a better understanding of lumbopelvic biomechanical behaviour according to the type of LBP is required. Our objectives were to identify differences in lumbopelvic rhythm (LPR) between subjects with acute low back pain (aLBP), axial spondyloarthritis (axSpA) and healthy subjects. As well as to identify correlations between LPR and sociodemographic and clinical data. In each group of 39 subjects, LPR total and by quartiles (Q) and metrological and clinical data were evaluated. No differences were found in relation to total flexion and LPR extension. However, study by Q showed less movement in aLBP compared to axSpA and healthy subjects at the Lumbar level in Q2 (p = 0.001), Pelvis in Q3 and Q4 and Trunk in Q3 (p=<0.001). In Q4 the aLBP moved the Trunk less than axSpA exclusively [-3,64°(95 % confidence interval - 6.53,-0.74), p = 0.011]. For the extension movement, the Pelvic motion of Q2 was lower for the aLBP group compared to axSpA group [-3,11°(-6.00,-0.22), p = 0.030], and Trunk motion of Q2 and Q3 (p = 0.001, p = 0.007, respectively), and Lumbar mobility of Q3 were also lower compared to axSpA and control groups (p = 0.031). Specific correlations were found for each group. aLBP with BMI, axSpA with metrology and Healthy subjects with age. Subjects with aLBP showed less lumbar, pelvic or trunk movement in Q2 and Q3 of trunk flexion and extension movements than axSpA and controls. RPL and its interrelationships with sociodemographic and clinical variables depend on the lumbar condition.