Adaptive Patterns of Movement during Downward Reach and Pick-up Movements in Knee Osteoarthritis Patients with Mild Low Back Pain

[Purpose] Patients with severe bilateral knee osteoarthritis (KOA) often suffer from low back pain (LBP). However, few studies have examined the relationship between LBP and KOA in downward reach and pick-up movements. [Subjects] Eight KOA patients with LBP (LBP group), 8 KOA patients without LBP (NLBP group), and 7 healthy participants (Control group), without osteoarthritis or low back pain, were recruited for this study. [Methods] All subjects were asked to pick up a bottle with one hand, placed at the diagonal on the opposite side of the body. A 3D motion analysis system was used to record trunk and lower limb movements. [Results] The knee flexion angle on the side ipsilateral to the bottle was significantly smaller in both KOA groups than in the controls in the downward reach and pick-up movements. KOA patients showed a significantly lower trunk flexion angle and greater pelvis anterior tilt angle than the controls. In addition, no significant differences were found between the LBP and NLBP group. [Conclusion] We suspect that severe knee pain due to OA determines the priority of movement in strategic planning for the execution of pick-up movements. The knee strategy was abandoned by our severe knee OA patients, even when they had mild LBP.