Responsiveness and interpretability of the Italian version of the Knee Outcome Survey − Activities of Daily Living Scale in patients with knee disorders

ObjectiveTo assess the responsiveness and interpretability (by the minimal important change [MIC]) of the Knee Outcome Survey - Activities of Daily Living Scale (KOS-ADLS) in patients with knee disorders and to evaluate potential differences between samples with surgical and with non-surgical history using both patient- and physiotherapist-reported perspectives.Study designClinimetric longitudinal study.SettingThree private physiotherapy clinics.Participants115 patients with knee disorders undergoing physiotherapy.InterventionParticipants completed the KOS-ADLS and other measurement instruments at baseline and after the treatment.Main measuresResponsiveness was assessed through hypothesis testing using effect sizes (ESs), standardised response means (SRM), change score correlations between KOS-ADLS and other measurement instruments, and area under the curve (AUC) values. Interpretability was assessed with MIC, determined using receiver operating characteristic (ROC)-based anchor methods via patient- and physiotherapist-reported Global Rating of Change. Responsiveness and MIC were provided for the total sample, sample with surgical history and sample with non-surgical history.ResultsKOS-ADLS demonstrated large ES (0.90) and SRM (1.03) values in the total sample, with better responsiveness in sample with surgical history patients. AUC values exceeded 0.70 across groups. Responsiveness was satisfactory as 91.7% hypotheses were confirmed. MIC values ranged from 8.5 to 18 points, with the highest estimates in the sample with surgical history patients and from the physiotherapist's perspective.ConclusionThe KOS-ADLS is a responsive and interpretable instrument for assessing change in knee-related function. Its findings vary by sample (sample with surgical history, sample with non-surgical history) rather than perspective (patient, physiotherapist).