Good Validity and High Internal Consistency of the Forgotten Joint Score-12 in Patients After Medial Opening Wedge High Tibial Osteotomy

Background: The Forgotten Joint Score-12 (FJS-12) was originally developed to assess awareness of an artificial joint. Medial opening wedge high tibial osteotomy (MOWHTO), an alternative surgical method of knee replacement, is a joint-preservation surgery; therefore, joint awareness should be used to evaluate its clinical results. However, FJS-12 has not been validated as a tool to evaluate the postoperative results of MOWHTO. This study aimed to validate FJS-12 in MOWHTO. Methods: Patients with bilateral knee surgery, previous knee surgery, flexion contracture >15 degrees, varus alignment >20 degrees, and patients without plate removal surgery were excluded. Finally, 71 knees of 71 patients were analyzed, with a mean follow-up of 34.5 months. The FJS-12 score and Knee Injury and Osteoarthritis Outcome Score (KOOS) were obtained, and the floor and ceiling effect of each score was investigated. Cronbach's alpha was calculated to determine the internal consistency of FJS-12. Spearman's correlation coefficients between FJS-12 and KOOS were calculated to assess convergent validity. Results: There were ceiling effects in 3 KOOS subscales (symptoms [25.4%], pain [15.5%], and activities of daily living [25.4%]) but not in FJS-12 (8.5%). No floor effect was noted in any patient-reported outcome measures. The total Cronbach's alpha was 0.9457 in FJS-12. FJS-12 showed moderate-to-strong positive correlations with all KOOS subscales (r = 0.64-0.72). Conclusion: FJS-12 showed a lower ceiling effect than KOOS and high internal consistency and convergent validity in patients following MOWHTO. With its low ceiling effect, FJS-12 was found to be useful for evaluating patients following MOWHTO. (C) 2021 Elsevier Inc. All rights reserved.