BackgroundKnee osteoarthritis (OA) represents a heavy burden for patients and the society as a whole. The Oxford Knee Score (OKS) is a well known tool to assess the quality of life in patients with Knee OA. The purpose of this study was to analyze the psychometric properties of the Spanish version of the OKS, including its reliability, validity, and responsiveness.MethodsProspective observational study that included 397 patients diagnosed with knee OA according to the criterion of the American Rheumatism Association, which were recruited in 3 different Spanish regions. Their self-perceived health-related quality of life (HRQL) was assessed through 3 questionnaires: a generic one (the EQ-5D-5 L) and two specific ones adapted to Spanish (the Western Ontario and McMaster Universities Osteoarthritis Index (WOMAC) and the Oxford Knee Score (OKS). The follow-up period was 6 months, and the acceptability of the OKS was evaluated, together with its psychometric properties, presence of ceiling and floor effects, validity, reliability, and sensitivity to change.ResultsThe OKS was fully answered in 99.5% of cases, with no evidence of ceiling or floor effects. Its factor structure can be explained in a single dimension. Its discriminating capacity was very good compared to the groups generated by the WOMAC and the EQ-5D-5 L. The correlation of the OKS with the dimensions of the latter questionnaires was around 0.7. The test-retest reliability was excellent (ICC 0.993; CI 95%: 0.990–0.995) and so was its internal consistency (Cronbach’s α = 0.920). The effect size was 0.7 for moderate improvements in the HQRL, which is similar to that of the dimensions of the WOMAC and greater than for the EQ-5D-5 L. The minimum clinically significant difference that was detected by the questionnaire was 6.1 points, and the minimum detectable change was 4.4 points.ConclusionsThe Spanish-adapted version of the OKS is a useful, valid tool for assessing the perceived HRQL in patients suffering from knee OA, with psychometric properties similar to the WOMAC, and that allows for discriminating the patient’s condition at a particular moment as well as for appraising changes over time.Electronic supplementary materialThe online version of this article (10.1186/s12955-017-0761-2) contains supplementary material, which is available to authorized users.

Objective Osteoarthritis of the lower limb (OALL) worsens health-related quality of life (HRQL), but this impact has not been quantified with standardized measures. We intend to evaluate the impact of OALL on HRQL through measures based on individual preferences in comparison to the general population. Methods A cross-sectional study was designed. A total of 6234 subjects aged 50 years or older without OALL were selected from the Spanish general population (National Health Survey 2011-12). An opportunistic sample of patients aged 50 years or older diagnosed with hip (n = 331) or knee osteoarthritis (n = 393), using the American Rheumatism Association criteria, was recruited from six hospitals and 21 primary care centers in Vizcaya, Madrid and Tenerife between January and December 2015. HRQL was measured with the EQ-5D-5L, and the results were transformed into utility scores. Sociodemographic variables (age, sex, social group, cohabitation), number of chronic diseases, and body mass index were

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