Reliability and validity of the Turkish version of the patellofemoral pain and osteoarthritis subscale of the KOOS

Background: Patellofemoral pain and patellofemoral osteoarthritis are highly prevalent knee disorders associated with pain and functional limitations. The subscale of the Knee Injury and Osteoarthritis Outcome Score for patellofemoral pain and osteoarthritis (KOOS-PF) was developed to evaluate patients with patellofemoral pain and osteoarthritis. Purpose: This study aims to translate the KOOS-PF into Turkish and assess its measurement properties. Methods: The Turkish version of the KOOS-PF was tested for reliability and validity in a convenience sample of 55 patients with patellofemoral pain and/or osteoarthritis. Reliability analyses were conducted through a retest 7–14 days later with a subgroup of 35 patients. The KOOS-PF was compared with Kujala’s Anterior Pain Scale (AKPS) and the Short Form-36 health survey (SF-36) to assess construct validity. Additionally, responsiveness analyses were performed on 29 patients who were followed up with a home-based exercise program three months later. Results: The Turkish version of KOOS-PF has high test-retest reliability (ICC2,1 = 0.96) and internal consistency (Cronbach’s α = 0.91). It has a very good correlation with the AKPS (r = 0.77) and the SF-36 physical component summary (r = 0.64) with no floor or ceiling effects. Responsiveness is confirmed by a good correlation with the global rating of change score (r = 0.51). The minimal clinically important change is 16.5 points, and the minimal important difference is 10.2. Conclusion: The Turkish version of the KOOS-PF is valid, reliable, and responsive for evaluating patients with patellofemoral pain and/or osteoarthritis.