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Background: In 2012, a new Knee Society Knee Scoring System (KSS) was developed and validated to address the needs for a scoring system that better encompasses the expectations, satisfaction, and physical involvement of a younger, more active population of patients undergoing TKA. Revalidating this tool in a separate population by individuals other than the developers of the scoring system seems important, because such replication would tend to confirm the generalizability of this tool., Questions/purposes: The purposes of this study were (1) to validate the KSS using a separate sample of patients undergoing primary TKA; and (2) to evaluate the internal consistency of the KSS., Methods: Intervention and control groups from a randomized controlled trial with no between-group differences were pooled. Preoperative and postoperative (6 weeks and 1 year) data were used. Patients with osteoarthritis undergoing primary TKA completed the patient-reported component of the KSS, Knee Injury and Osteoarthritis Outcome Score (KOOS), SF-12, two independent questions about expectations of surgery, and the Patient Acceptable Symptom State (PASS) single-question outcome. This study included 345 patients with 221 (64%) women, an average (SD) age of 64 (8.6) years, a mean (SD) body mass index of 32.9 (7.5) kg/m, and 225 (68%) having their first primary TKA. Loss to followup in the control group was 18% and loss to followup in the intervention group was 13%. We quantified cross-sectional (preoperative scores) and longitudinal validity (pre- to postoperative change scores) by evaluating associations between the KSS and KOOS subscales using Spearman's correlation coefficient. Preoperative known-group validity of the KSS symptoms and functional activity score was evaluated with a one-way analysis of variance across three levels of physical health status using the SF-12 Physical Component Score. Known-group validity of the KSS expectation score was evaluated with an unpaired t-test by comparing means across known expectation groups. Known-group validity of the KSS satisfaction score was evaluated with an unpaired t-test by comparing means across yes/no response groupings of the PASS single-question outcome. Internal consistency for each KSS subscale was evaluated with Cronbach's α., Results: Cross-sectional validity (ie, associations at a single point in time) was supported because correlation coefficients between KSS symptoms, functional activities, and satisfaction scores and scores on the KOOS pain subscale ranged from 0.60 to 0.73 (all correlations p < 0.01). Values were similar for associations with the KOOS function in the activities of daily living (ADL) subscale (0.66-0.69) and less (0.41-0.58) for correlations with the other three KOOS subscales. Longitudinal validity (ie, associations of change scores between two time points) was also supported because correlation coefficients between KSS symptoms, functional activities, and satisfaction change scores and the KOOS pain and ADL change scores varied from 0.63 to 0.73. Correlation coefficients were lower for the other three KOOS subscale change scores, suggesting a weaker relationship with KOOS symptoms (0.48-0.53), sports (0.47-0.51), and quality of life (0.60-0.65) (all correlations p < 0.01). Known-group validity (ie, differences between groups that are known to differ on a given characteristic) was confirmed by between-group differences for the symptoms and functional activities score comparisons as well as the comparisons with the expectations and satisfaction scores of the KSS (all p < 0.01). Cronbach's α (ie, association among subscale items) varied from 0.68 (discretionary activities) to 0.94 (postoperative expectations) across four KSS subscales., Conclusions: Moderate-sized correlation coefficients and consistent differences between known groups support the validity of the KSS. Internal consistency values were also acceptable. The patient-reported subscales of the KSS are a valid and internally consistent outcome assessment for TKA.

Unlabelled: Despite substantial advances in primary TKA, numerous studies using historic TKA implants suggest only 82% to 89% of primary TKA patients are satisfied. We reexamined this issue to determine if contemporary TKA implants might be associated with improved patient satisfaction. We performed a cross-sectional study of patient satisfaction after 1703 primary TKAs performed in the province of Ontario. Our data confirmed that approximately one in five (19%) primary TKA patients were not satisfied with the outcome. Satisfaction with pain relief varied from 72-86% and with function from 70-84% for specific activities of daily living. The strongest predictors of patient dissatisfaction after primary TKA were expectations not met (10.7x greater risk), a low 1-year WOMAC (2.5x greater risk), preoperative pain at rest (2.4x greater risk) and a postoperative complication requiring hospital readmission (1.9x greater risk)., Level of Evidence: Level II, prognostic study. See Guidelines for Authors for a complete description of levels of evidence.

Unlabelled: Total knee arthroplasty now exceeds total hip arthroplasty as the most commonly performed joint replacement. Projections suggest the need for revision knee arthroplasty in the future will produce an immense economic burden. The excellent cost effectiveness of primary knee arthroplasty has been well established. This article explores the cost effectiveness of revision knee arthroplasty, and makes a comparison of costs between different international health care systems. While revision knee arthroplasty is more costly, technically difficult, and complicated than primary knee arthroplasty, it is still a cost effective means of improving function, pain relief, and quality of life. The role of national arthroplasty registries will be important in guiding decision making toward reducing the requirements for revision surgery., Level of Evidence: Prognostic study, level II-1 (prospective study). See Guidelines for Authors for complete description of levels of evidence.