Muscle Activation and Mobility After Robotic Total Knee Arthroplasty: Insights from Early Postoperative Recovery

Background: Robot-assisted total knee arthroplasty (TKA) has gained attention for its ability to improve surgical precision, optimize component alignment, and potentially enhance functional outcomes. Despite these advantages, early postoperative deficits, particularly in quadricep activation and the range of motion (ROM), remain common and can delay recovery. The objective of this study was to investigate early postoperative differences in quadricep muscle activation and the ROM between the operated and non-operated sides following robot-assisted TKA. Methods: A total of 101 participants (50 females, 51 males) were included in the study. Surface electromyography (sEMG) was recorded from the vastus lateralis and vastus medialis during an active knee extension test and a 4-m walking test. The ROM was assessed during gait. A linear mixed model was employed with operated side and sex as factors. Results: Significant differences were observed in quadricep muscle activation and the ROM between the operated and non-operated sides. During the knee extension test, males exhibited significantly higher vastus lateralis activity on the non-operated side (mean difference = 174 µV, 95% confidence interval (CI) [90, 258], p < 0.001) and females showed a similar pattern (mean difference = 238 µV, 95% CI [152, 324], p < 0.001). Additionally, vastus medialis activation was significantly higher on the non-operated side for both males (mean difference = 102 µV, 95% CI [34, 169], p = 0.003) and females (mean difference = 137 µV, 95% CI [47, 226], p = 0.003). During the 4-m walking test, females displayed a significantly reduced sagittal-plane ROM on the operated side (mean difference = 7.691°, p = 0.041) whereas no significant ROM differences were found in males (p > 0.903). Conclusions: Robot-assisted TKA patients exhibit significant early postoperative asymmetries in quadricep activation and the gait ROM, particularly among females.