Validation of the Spanish Version of the Knee Injury and Osteoarthritis Outcome Score (KOOS) for Elderly Patients With Total Knee Replacement

The purpose of this study was to validate the Knee Injury and Osteoarthritis Outcome Score (KOOS) for elderly patients who undergo total knee replacement (TKR). The validated Spanish versions of the KOOS and Medical Outcomes Study 36‐Item Short‐Form Health Survey (SF‐36) questionnaires were applied to 137 patients (mean age 72.3, SD 7.5 years). Test–retest data were collected with an intermediate period of 1–2 weeks. To evaluate the clinimetric properties of the KOOS, internal consistency (Cronbach’s α), reproducibility (intraclass correlation coefficient [ICC]), construct validity (Spearman’s correlation), responsiveness (effect sizes [ES], and standardized response mean [SRM]), and floor and ceiling effects (<15%) were assessed. As result, Cronbach’s coefficients of the KOOS subscales ranged from 0.78 to 0.93, and ICC from 0.76 to 0.91. Construct validity was supported by the confirmation of the three predefined hypotheses involving expected correlations between KOOS subscale and SF‐36 physical health subscales. Spearman’s correlations were strong between KOOS Pain and SF‐36 Bodily Pain (r = 0.81), KOOS Pain and SF‐36 Physical Functioning (r = 0.67), KOOS activities of daily living (ADL) and SF‐36 Bodily Pain (r = 0.69), KOOS ADL and SF‐36 Physical Functioning (r = 0.74), and KOOS Sports/Recreation and SF‐36 Physical Functioning (r = 0.76). Responsiveness at 1 year after TKR was large with the ES ranging from 0.81 to 2.12, and the SRM from 0.70 to 1.91. Floor and ceiling effects were low. In conclusion, the Spanish version of KOOS has successful psychometric characteristics and is a reliable and valid instrument for assessment of patient‐relevant outcomes in elderly patients with advanced OA who undergo TKR. © 2019 Orthopaedic Research Society. Published by Wiley Periodicals, Inc. J Orthop Res 37:2157–2162, 2019