Agreement between methods to assess the construct 'knee pain during walking' in knee osteoarthritis patients: a cross-sectional study

s / Osteoarthritis and Cartilage 20 (2012) S54–S296 S161 disability, and limiting progression of joint damage. When conservative treatment fails and joint preserving surgery is not or no longer indicated, knee replacement of the affected joint becomes necessary. A proper selection of patients for total knee replacement surgery is crucial in the light of the exponentially growing numbers with its socioeconomic impact. The present study evaluated potential radiographic and clinical predictors for clinical outcome of knee replacement surgery in a cohort of patients with end-stage knee OA treated in regular practice in an orthopedic department of a general hospital in the Netherlands. Methods: Patients (172) with severe OA who were eligible for total knee replacement surgery in a general hospital were included. Demographics, clinical, and radiographic data were collected.WOMAC datawere collected prospective pre-treatment, and after surgery (post-treatment). OARSIOMERACT response criteria based onWOMAC questionnaires were used to evaluate clinical success. Severity of radiographic joint damage was evaluated according to Kellgren & Lawrence and Altman atlas. Pre-treatment characteristics associated with responder status were investigated using multivariate logistic regression analyses. Results:Patients showedonaveragea clear improvement inWOMACscores at a mean of 18 months post-treatment (33.0 20.0 improvement in WOMAC pain).BasedonWOMACresponse criteria 55%of thepatientswere classifiedas responders. Inmultivariate logistic regression, youngerage (OR1⁄40.930;95%CI: 0.864-1.002), more severe pain (OR1⁄40.966; 95%CI: 0.937-0.997) and more radiographic damage (OR1⁄43.456; 95%CI: 1.568-7.618) was associated with good response. Results were similar when patients with missing outcomes were classified as non-responders or responders in a sensitivity analysis. Conclusions: This study shows that still a significant number of patients do not have a good response to joint replacement surgery. A good response was clearly associated with more severe radiographic joint damage and possibly with age and WOMAC pain at time of operation. These results need further validation in larger cohorts and might become of use to a more accurate patient selection for knee replacement surgery. 317 AGREEMENT BETWEEN METHODS TO ASSESS THE CONSTRUCT 'KNEE PAIN DURING WALKING' IN KNEE OSTEOARTHRITIS PATIENTS: A CROSS-SECTIONAL STUDY L. Klokker , R. Christensen , R. Osborne , J. Aaboe , H. Bliddal , M. Henriksen . 1 Parker Inst., Copenhagen, Denmark; 2 Inst. of Sports Sci. and Clinical Biomechanics, Faculty of Hlth.Sci., Univ. of Southern Denmark, Odense, Denmark; 3 Population Hlth.Strategic Res. Ctr., Sch. of Hlth.and Social Dev., Faculty of Hlth., Deakin Univ., Burwood, Australia; 4 Faculty of Hlth.Sci., Univ. of Copenhagen, Copenhagen, Denmark Purpose: Measures of pain and function are core outcomes in knee osteoarthritis (OA) in both clinical practice and research. In research settings, questionnaires are commonly used, but their applicability in clinical settings is limiteddue to the lack of guidelines for theirapplication and the inabilityof multidimensional questionnaires to detect changes on an individual level. In clinical rehabilitation settings, performance measures are likely to be used, although no available surveys clarify the actual application. Performance tests might relate more specifically to a sensory aspect of pain than multidimensional questionnaires, which would correspond well to the target of pharmacological and exercise based treatment and therefore be more specific in evaluating the intended impactsof an intervention. Aperformance test with subsequent pain intensity scoringmight serve as a feasiblemethod of assessing a sensory aspect of pain, but to establish if the suspected divergence between the underlying constructs exists, the agreement between a performance pain test and a questionnaire remains to be studied. The purpose of this study was to assess the agreement between a performance pain test and a widely used multidimensional questionnaire (the Knee injury and Osteoarthritis Outcome Score, KOOS). Methods: Cross sectional data from 143 patients with knee OA included in a prospective weight loss study (the CAROT study) were analysed. All participants rated their target knee pain, on a 100 mmvisual analogue scale (VAS) after walking 150-200 m at a self-selected pace in a gait laboratory. KOOS was completed within one week prior. The KOOS pain subscale and item 5 of the KOOS pain subscale (“amount of knee pain experienced during walking on flat surface the last week”, KOOSp05) were selected for analysis. Distributions of VAS scores within the KOOSp05 response categories were describedand scoreswere comparedusingSpearman correlation. To support interpretability of the results, the KOOS pain subscale score was reversed to the same polarity as the VAS score (i.e. 01⁄4 no pain and 1001⁄4 extreme pain) and agreement was estimated using Limits of Agreement. Results: There was a moderate correlation between VAS and KOOSp05 (r 1⁄4 0.5, p<0.001), illustrated by a wide range of VAS scores within the KOOS response categories (figure 1). The mean difference for pain scores assessed withVASandKOOSpain subscale respectivelywas 18.8 (SD16.6),with Limits ofAgreement from-13.6 to 51.3 (figure 2). In general, higher pain scoreswere reported with the questionnaire than after the performance test. Conclusions:Thedisagreementbetween theperformancepainmeasure and theKOOSpain subscale togetherwith themoderate associationbetweenVAS and KOOSp05 item scores suggest that different constructs of pain are measured, indicating that a combined performance and pain assessment method could contribute with valuable information when evaluating treatment effects, though further validation studies are required.