Responsiveness and the minimal important change of Knee injury and Osteoarthritis Outcome Score in Persian patients with knee osteoarthritis following physiotherapy intervention

Abstract

Introduction: Knee injury and Osteoarthritis Outcome Score (KOOS) is a widely used patient-reported outcome measure designed for patients with knee osteoarthritis.Purpose: To evaluate responsiveness and determine minimal important change (MIC) for Persian-version of KOOS in patients with knee osteoarthritis following physiotherapy intervention.Method: One hundred and forty-six consecutive patients with knee osteoarthritis, undergoing 4-week physiotherapy completed KOOS alongside Oxford Knee Score at baseline and at 4-week follow-up. Patients also rated their overall changes on an external anchor at follow-up. Responsiveness was examined in two ways: by testing four hypotheses regarding pre-defined correlations between change scores of KOOS subscales and Oxford Knee Score and external anchor, and by calculating receiver operating characteristic (ROC) curve. MIC was determined by identifying an optimal cutoff on ROC curve.Results: KOOS appeared to be responsive, as all expected hypotheses were accepted. Also, all subscales showed area under the curve (AUC) > 0.70. The MIC values reflecting improvement for Pain, Symptoms, Activities of Daily Living (ADL), Sports and Recreation (Sport/Rec), and Quality of Life (QoL) subscales were 15, 12.5, 15.5, 17.5, 12.5 points, respectively.Conclusions: All subscales of KOOS have adequate responsiveness and are able to measure the change in patients with knee osteoarthritis following a 4-week physiotherapy intervention.