Preliminary Validity and Reliability Evidence for a Derived 12-Item Greek Short-Form Model of the Quality Indicators for Physiotherapy Management of Hip and Knee Osteoarthritis (QUIPA)

Background/Objectives: Osteoarthritis of the hip and/or knee is a major contributor to pain, disability, and reduced quality of life. The aim of this study was to provide preliminary validity and reliability evidence for a Greek adaptation of the Quality Indicators for Physiotherapy Management of Hip and Knee Osteoarthritis (QUIPA) questionnaire. Methods: This cross-sectional methodological study involved cross-cultural adaptation and psychometric evaluation of the Greek QUIPA in 90 adults aged 45–65 years with hip and/or knee osteoarthritis attending private physiotherapy clinics. Participants completed the questionnaire twice, seven days apart. Structural validity was explored using exploratory factor analysis, and exploratory subgroup analyses by age and sex were also conducted. Internal consistency, categorical item-level test–retest reliability, total-score test–retest reliability, and floor/ceiling effects were assessed. Results: Exploratory factor analysis of the initial 18-item pool suggested a three-factor 12-item solution explaining 51.5% of the total variance, with eigenvalues of 3.11, 1.58, and 1.49. Internal consistency was borderline for the total score (Cronbach’s alpha = 0.675) and the first factor (alpha = 0.662), and poor for the second (alpha = 0.424) and third (alpha = 0.598) factors. Item-level observed agreement ranged from 79.7% to 97.8%, with Cohen’s kappa values ranging from 0.580 to 0.887. Total-score test–retest reliability was good (ICC = 0.829, 95% CI = 0.748–0.896), although the total proportion-positive score increased by 5.6 percentage points at retest. Ceiling effects were observed for Q1, Q7, and Q8. Conclusions: The present study provides preliminary validity and reliability evidence for a derived 12-item Greek QUIPA short-form model. However, given the marginal sampling adequacy, low-to-moderate communalities, six-item reduction from the original 18-item questionnaire, categorical item properties, and borderline-to-poor internal consistency of some factors, the findings should be interpreted cautiously. At present, the Greek QUIPA is best interpreted using the total proportion-positive score, whereas factor-level scores should be treated as exploratory. Independent confirmatory factor analysis and further validation in larger and more diverse samples are required.