Acute and mid-term (six-week) effects of an ankle-foot-orthosis on biomechanical parameters, clinical outcomes and physical activity in knee osteoarthritis patients with varus malalignment

Abstract

BackgroundKnee osteoarthritis (KOA) is a painful disease commonly caused by high loads on the articular cartilage. Orthotic interventions aim to reduce mechanical loading, thereby alleviating pain. Traditional orthotics appear effective, but high drop-out rates have been reported over prolonged periods. Research questionThe aim of this study was to examine the effect of a novel ankle-foot orthosis (AFO) on gait parameters, physical function and activity of KOA patients. Methods29 clinically diagnosed KOA patients with varus malalignment wore an AFO for 6 weeks. Prior to and after the intervention period, 3D gait analysis, physical function tests and the KOOS questionnaire were administered. Physical activity was objectively assessed with accelerometers. ResultsThe AFO immediately reduced the first peak of the knee adduction moment (KAM) and the KAM impulse by 41% and 19%. The knee flexion moment (KFM) was increased by 48%. After six weeks, the first KAM peak and KAM impulse were decreased by 27% and 19% while using the AFO. The KFM was increased by 71%. Furthermore, patients completed the functional tests faster (1.4–2.6%). The KOOS scores decreased significantly. No significant differences were found in physical activity parameters. SignificanceThe six-week AFO application significantly reduced the KAM. The patients’ physical function appeared improved; yet these improvements were only minor and therefore arguably clinically irrelevant. The KFM appeared to be negatively affected after six weeks, as were the scores on the KOOS subscales. In summary, even though the AFO reduced the KAM and improved physical function, the clinical benefit for KOA patients with varus malalignment after the 6-week AFO application is debatable.