Correlation of the Forgotten Joint Score and Oxford Knee Score in Patients Undergoing Primary Total Knee Arthroplasty: A Cross-sectional Study in a Tertiary Care Center

Aim and background: Total knee arthroplasty (TKA) is a commonly performed surgical procedure for end-stage knee arthritis.Conventional patient-reported outcome measures (PROMs), such as the Oxford knee score (OKS), are limited by ceiling effects and may inadequately assess joint awareness.The forgotten joint score (FJS)-12 was developed to evaluate the patient's ability to "forget" the artificial joint during daily activities.This study evaluated the validity, reliability, ceiling effect, and correlation of the modified FJS-12 with the OKS following primary TKA.Materials and methods: This cross-sectional study included 217 knees evaluated 6-18 months after primary TKA.Patients completed the modified FJS-12 and OKS questionnaires following institutional ethics approval.Internal consistency was assessed using Cronbach's alpha, construct validity using Pearson's correlation coefficient, and ceiling effect by calculating the proportion of patients achieving scores within 15% of the maximum possible score.Statistical analysis was performed using IBM Statistical Package for the Social Sciences (SPSS) version 26 with significance set at p < 0.05.Results: Both scoring systems demonstrated excellent internal consistency reliability, with Cronbach's alpha values of 0.925 for FJS-12 and 0.951 for OKS.Pearson's correlation coefficient between FJS-12 and OKS was 0.34, indicating a weak positive correlation.The FJS-12 demonstrated a low ceiling effect of 1%, whereas the OKS demonstrated a high ceiling effect of 68.2%.Significant item-to-total correlations supported construct validity of both questionnaires. Conclusion:The modified FJS-12 is a valid and reliable PROM with a low ceiling effect after TKA.It better evaluates joint awareness and may more effectively distinguish excellent postoperative outcomes in high-functioning patients.Clinical significance: Incorporating the modified FJS-12 alongside conventional PROMs such as the OKS provides complementary information regarding postoperative joint awareness and may improve the assessment of excellent outcomes following TKA.