Factors Predicting the Forgotten Joint Score After Total Knee Arthroplasty

Abstract

Background: We recently developed the forgotten joint score 12 (FJS-12), a tool to assess joint awareness in everyday life. It is unknown whether patient factors predicting the outcome of the FJS-12 after total knee arthroplasty (TKA) exist.

Methods: Five hundred forty cases of TKA were analyzed. Objective clinical results were obtained for range of motion, stability, and alignment. Patient-reported outcome was assessed using the FJS-12. Baseline data and complications were recorded. Cluster analysis based on FJS-12, postoperative flexion, and age resulted in 3 groups: poor outcome (88 patients), good outcome (340 patients), and excellent outcome (118 patients). The characteristics of "poor" compared to "excellent" clusters were studied more closely using bivariate comparative tests and logistic regression.

Results: We could find that male patients around 63 years with a lower body mass index were most likely to be allocated to the cluster "excellent" (defined as high FJS-12 and high postoperative flexion). Preoperative extension and flexion, stability, varus/valgus alignment, surgery prior TKA, or comorbidities were not predictive for the FJS-12 at 1 year follow-up.

Conclusion: We identified 3 preoperative patient-related factors that may predict the FJS-12 after TKA: body mass index, age, and gender. These findings can be used to guide decision-making and important preoperative discussions on expectations after TKA.

Keywords: body mass index; forgotten joint score 12; patient-reported outcome; predictors; total knee arthroplasty.