Validation of the Spanish version of the Oxford knee score and assessment of its utility to characterize quality of life of patients suffering from knee osteoarthritis: a multicentric study

Abstract

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.

Mapping analysis to predict EQ-5D-5 L utility values based on the Oxford Hip Score (OHS) and Oxford Knee Score (OKS) questionnaires in the Spanish population suffering from lower limb osteoarthritis

“…Patients with hip and knee OA completed the Spanish (Spain) version of the OHS [23,25] and OKS [24,26], respectively. Both questionnaires are self-administered questionnaires that can be answered via "face-to-face" interviews or mailed in by the patient after completion.…”

“…The final score is calculated by summing up the individual scores and ranges from 0 to 48, with 48 the best possible outcome [34]. The scores were developed to assess the outcome of hip and knee replacements, but they have also been used to assess changes in the basal situation of a patient with hip or knee OA [25,26,34]. The questionnaires were completed at the clinic, after the inclusion of patients and at the 6-month follow-up visit (Additional file 1 shows all the questions in the Spanish (Spain) version of the OHS, and Additional file 2 shows all the OKS questions in its Spanish (Spain) version).…”

“…Other questionnaires, such as the Knee Society Clinical Rating System (KSS) [19,20] and the Knee Injury and Osteoarthritis Outcome Score (KOOS) [21,22], specifically assess HRQoL in patients with knee OA. The Oxford Hip Score (OHS) [23] and Oxford Knee Score (OKS) [24] are questionnaires designed to assess the outcome following hip or knee replacement; they have recently been validated in Spanish for the population in Spain suffering from hip or knee OA whether or not undergoing surgical procedures [25,26]. Although OHS and OKS scores do not inform about preferences on the health states, mapping procedures have been developed to predict utilities based on EQ-5D using scores from the OKS and OHS in other countries [27,28].…”

Impact of lower limb osteoarthritis on health-related quality of life: A cross-sectional study to estimate the expressed loss of utility in the Spanish population

“…The responses to the VAS of the EQ-5D-5L ranged from 0 to 100 for both the general population and the patients with OALL (both hip and knee). Table 3 shows the level of severity for patients with osteoarthritis of the knee or hip as measured with the WOMAC and the OHS/OKS [30,32,33]. Those with osteoarthritis of the knee more frequently had bilateral involvement, but those with osteoarthritis of the hip more commonly showed concomitant involvement of the other large lower limb joint.…”

“…Each scale consists of 12 questions, and the scores, which range from 0 to 48 points, classify the clinical situation of osteoarthritis patients in 4 groups: excellent (> 41 points), good (between 34 and 41 points), moderate (between 27 and 34 points) and poor (<27 points) [31]. The Spanish versions of the OKS and OHS questionnaires have also been validated [32,33].…”