Purpose: To evaluate the difference in post-operative knee awareness between knees in patients undergoing bilateral simultaneous total knee arthroplasty (TKA) and to assess factors predicting high or low knee awareness.
Methods: This study was conducted on 99 bilateral simultaneous TKAs performed at our institution from 2008 to 2012. All patients received one set of questionnaires [Forgotten Joint Score (FJS) and Oxford Knee Score (OKS)] for each knee. Based on the FJS, the patients' knees were divided into two groups: "best" and "worst" knees. The median of the absolute difference in FJS and OKS within each patient was calculated. Multivariate linear regression was performed to identify factors affecting FJS.
Results: The difference between knees was 1 point (CI 0-5) for the FJS and 1 point (CI 0-2) for the OKS. The FJS for females increased (decreasing awareness) with increasing age. Males had the highest FJS (lowest awareness) at the age of 67. An increase in the FJS (lower knee awareness) of 12.0 points was found for Kellgren-Lawrence (K-L) grades 3 + 4 compared with K-L grades 1 + 2. A preoperative anatomical alignment of 3° valgus resulted in the lowest FJS (highest knee awareness) with decreasing knee awareness for decreasing tibio-femoral angles. Post-operative alignment did not significantly affect FJS.
Conclusion: Knee awareness did not differ significantly between the "best" and the "worst" knee. Bilateral simultaneous TKA can be performed without compromising the result in one of the knees. Knee awareness after primary TKA was influenced by age, gender, preoperative knee alignment, and severity of OA.
Level of evidence: III.
Keywords: Arthroplasty; FJS; Forgotten Joint Score; Osteoarthritis; Outcome; TKA.