What is the Responsiveness and Respondent Burden of the New Knee Society Score?

• Published in: Clinical orthopaedics and related research 2017-09, Vol.475 (9), p.2218-2227
• Main Authors: Maniar, Rajesh N., Maniar, Parul R., Chanda, Debashish, Gajbhare, Dnyaneshwar, Chouhan, Toral
• Format: Article
• Language: English
• Subjects: Aged; Aged, 80 and over; Arthroplasty, Replacement, Knee - methods; Arthroplasty, Replacement, Knee - statistics & numerical data; Clinical Research; Conservative Orthopedics; Female; Follow-Up Studies; Humans; Knee; Longitudinal Studies; Male; Medicine; Medicine & Public Health; Middle Aged; Orthopedics; Patient Reported Outcome Measures; Patient Satisfaction - statistics & numerical data; Postoperative Period; Preoperative Period; Reproducibility of Results; Severity of Illness Index; Sports Medicine; Surgery; Surgical Orthopedics; Surveys and Questionnaires - standards; Time Factors; Treatment Outcome; Validity
• ISSN: 0009-921X; 1528-1132
• DOI: 10.1007/s11999-017-5338-1

Background Although the new Knee Society score (NKSS) has been validated by a task force, a longitudinal study of the same cohort of patients to evaluate the score’s responsiveness and respondent burden has not been reported, to our knowledge. Questions/Purposes We analyzed the NKSS for (1) responsiveness; (2) respondent burden; and (3) convergent validity in 148 patients studied longitudinally during more than 1 year. Methods During an 8-month period, 165 patients underwent TKA by the same surgeon at our institution, of whom 148 (90%) completed this study; the others were excluded because of distance to travel or loss to followup at the specified time. The NKSS, WOMAC, and SF-12 were completed by each patient 1 day before surgery and at 3 and 12 months postoperatively. At the same times, the original KSS (OKSS) which is designed as an observer’s assessment, was completed by the same orthopaedic fellow for all patients. Responsiveness of the NKSS was assessed by determining effect size, standardized response mean (SRM), and ceiling and floor effects. Respondent burden was assessed through time to completion recorded in minutes and ease of completion which was measured objectively on a Likert scale of 1 to 5 by the patients. Convergent validity was assessed by correlating the NKSS with the WOMAC, SF-12, and OKSS (current, widely used scales) by Pearson’s correlation coefficient. Results Effect size was largest (2.83 and 3.38) and SRM was highest (2.29 and 2.68) for the NKSS at 3 and 12 months respectively, indicating the NKSS to be the most-responsive score followed by the OKSS, WOMAC, and SF-12. The NKSS exhibited no ceiling and floor effects. The NKSS took a longer time to complete (5.49 ± 3.56 minutes) compared with the WOMAC (4.64 ± 3.19 minutes) and SF-12 (4.35 ± 3.27 minutes). The mean difference in time taken for the NKSS versus the WOMAC was 0.85 minutes (95% CI, 0.54–1.17 minutes; p < 0.001) and the mean difference for the NKSS versus the SF-12 was 1.14 minutes (95% CI, 0.76–1.15 minutes; p < 0.001). Its ease of completion generally was comparable to that of the WOMAC and SF-12. Convergent validity showed a strong correlation (r > 0.6; p < 0.001) of the NKSS with the WOMAC at all times and moderate to strong correlation (r = 0.4–0.6; p < 0.001) with the SF-12 and OKSS at the first two assessments, which became strong (r > 0.6; p < 0.001) at 12 months. Conclusions The NKSS exhibited greater responsiveness than the WOMAC, SF-12, and OKSS scales and s