Consistent differences in lumbar spine alignment between low back pain subgroups and genders during clinical and functional activity sitting tests

Subgroups of people with low back pain display differences in their lumbar alignment during tests from a clinical examination. However, it is unknown if subgroups display the same patterns during a functional activity test and if gender influences subgroup-related differences. Test if differences in lumbar alignment between two LBP subgroups are 1) present during a functional activity test of preferred sitting and 2) independent of gender. Cross-sectional. 154 participants with chronic low back pain were classified based on the Movement System Impairment Classification System by a physical therapist. Participants performed a functional activity test of preferred sitting and clinical tests of maximum flexed and extended sitting. 3D marker co-ordinate data were collected. Sagittal plane lumbar alignment, indexed by lumbar curvature angle, was calculated. A three-way mixed effect analysis of variance was used to examine effects of test, subgroup, gender, subgroup × test, gender × test and subgroup × gender. The lumbar rotation with extension subgroup [LCA = −8.0° (−9.5,-6.5)] displayed a more extended lumbar alignment than lumbar rotation [LCA = −5.9° (−7.4,-4.4)]. Women [LCA = −10.7° (−12.3,-9.2)] displayed a more extended lumbar alignment than men [LCA = −3.2° (−4.7,-1.7)]. There was a significant gender × test interaction (p = 0.01). The subgroup × test (p = 0.99) and subgroup × gender (p = 0.76) interactions were not significant. LBP subgroup differences in lumbar alignment are present during preferred sitting. Gender-related differences in lumbar alignment are not driving subgroup differences. These findings highlight the need to use patient-specific clinical characteristics to guide treatment of a functional activity of preferred sitting limited due to low back pain. •Low back pain subgroups differ in lumbar alignment during sitting tests.•Men and women differ in lumbar alignment during sitting tests.•Gender does not drive low back pain subgroup differences in lumbar alignment.•Clinical characteristics can be used to guide treatment of functional activities.