Responsiveness and minimally important differences for selected Persian-version of outcome measures used in patients with patellofemoral pain syndrome

Abstract

Purpose: To investigate the responsiveness and determine the minimally important differences (MID) of Persian versions of the Kujala patellofemoral scale (KPS), lower extremity functional scale (LEFS), and functional index questionnaire (FIQ) in patients with patellofemoral pain syndrome (PFPS). Method: Outcome measures including the Persian KPS, LEFS, and FIQ were administered to 233 patients at baseline and then again 4 weeks after physiotherapy. Moreover, the 7-point global rating scale was completed by the patients at 4 weeks. Responsiveness was evaluated using the correlation analysis and the receiver operating characteristics (ROC) method. Results: Correlation analysis showed that the relationship of all outcome measures with the global rating scale falls within the fair range of relationship (Gamma = 0.26–0.40). Moreover, the results of ROC analysis showed that the all outcome measures have acceptable high responsiveness index. Furthermore, the MIDs of 9.5, 4.5, and 1.5 points were obtained for the Persian KPS, LEFS, and FIQ, respectively. Conclusions: The Persian-versions of all outcome measures are responsive for evaluating change following physiotherapy intervention. The MID values obtained in this study will help the clinicians and researchers to determine if a patient with PFPS has experienced a true change following a physiotherapy intervention.Implications for RehabilitationPersian-versions of the KPS, LEFS, and FIQ can be used as three “responsive” outcome measures in clinical studies of patients with patellofemoral pain syndrome (PFPS).These assessment tools have clinical relevance for rehabilitation specialists working on patients with PFPS.The minimally important differences provide valuable information for the clinicians and researchers to make decision about the identification of a clinical change in health status of patients with PFPS.