BACKGROUND: Excessive and early lumbopelvic motion during functional tasks is associated with increased pain and symptoms in people with low back pain. The purpose of the current study was to compare lumbopelvic and lower extremity movements in two subgroups of chronic low back pain sufferers and healthy subjects during a stair descending task based on a movement system impairment model. MATERIAL AND METHODS: A clinical examination was conducted to assign people with low back pain to movement system impairment-based subgroups. A control group included 18 healthy subjects, a lumbar Rotation with Flexion group included 12 subjects, and a lumbar Rotation with Extension group included 16 subjects. Differences in kinematics data between the groups were recorded during a stair descending task using a 7-camera 3-dimensional motion capture system. RESULTS: In the lumbar Rotation with Flexion group, the onset of lumbar movement occurred earlier than in the control group (p = 0.043). In the lumbar Rotation with Flexion group, axial and frontal plane rotation of the pelvis and lower extremity were significantly greater than in the control group. Mean differences between the lumbar Rotation with Extension and control group were minimal for the motion assessed. CONCLUSION: Early and excessive lumbopelvic movement and more axial rotation in the lower extremities during a stair descending task were found in the lumbar Rotation with Flexion subgroup, which can be an important factor contributing to the development or persistence of low back pain in this group.