Noise after total knee arthroplasty has limited effect on joint awareness and patient-reported clinical outcomes: retrospective study

BACKGROUND: Some patients complain of noise after total knee arthroplasty (TKA). Controversy still exists on how the noise affects the clinical outcomes, including joint awareness, after TKA. The Forgotten Joint Score—12 (FJS-12) measures the clinical outcomes focusing on joint awareness after surgery. The Knee Society Scoring System—2011 (KSS-2011) includes questionnaires for satisfaction, expectation, and functional activities. The aim of this study is to clarify the relationship among FJS-12, KSS-2011, and the noise. Furthermore, the relationship between FJS-12 and KSS-2011 was validated. METHODS: Using FJS-12 and KSS-2011, 295 knees from 225 patients who underwent TKA were retrospectively evaluated. Noise perception was evaluated by a questionnaire with five grades, a method that follows the questionnaire form of FJS-12 (“Are you aware of the noise of your artificial joint?”; never, almost never, seldom, sometimes, mostly). Correlations among FJS-12, KSS-2011, and noise were analyzed. The patients were divided into four groups based on the mechanism of their implant [cruciate retaining, posterior stabilized, cruciate sacrificed, and bicruciate stabilized (BCS)]. FJS-12, KSS-2011, and noise were compared among the groups. RESULTS: A strong correlation was found between FJS-12 and total score of KSS-2011 (0.70; P < 0.001). FJS-12 correlated with KSS-2011 subcategories of “symptoms,” “satisfaction,” and “standard activities,” with correlation coefficients at approximately 0.60. Noise had weak correlations with FJS-12 (0.28; P < 0.001) and KSS-2011 (0.20 P < 0.001). In comparing the TKA mechanisms, BCS had remarkably better KSS-2011 and greater movement range but worse noise scores. CONCLUSIONS: Noise perception after TKA had limited effect on joint awareness and clinical outcomes. FJS-12 correlated strongly with KSS-2011 and associated with satisfaction, residual symptoms, and daily activities, as assessed by KSS-2011 subscores. TRIAL REGISTRATION: This study was approved by the Medical Ethical Committee of the Tokyo Women’s Medical University (approval number: 4681 on March 2, 2018).