Postoperative anterior knee pain in robot assisted total knee arthroplasty: a propensity score matching analysis

Anterior knee pain (AKP) remains a prevalent complication following total knee arthroplasty (TKA), affecting 4-60 % of patients. While robot-assisted TKA (RA-TKA) has demonstrated superior precision in prosthesis alignment compared to conventional manual TKA in the medium- and long-term, its impact on postoperative AKP remains underexplored. This study aimed to evaluate the medium- and long-term effects of RA-TKA on AKP intensity, functional outcomes, and knee mobility compared to CM-TKA.

In this retrospective cohort study, obese patients undergoing primary TKA for Kellgren-Lawrence grade 4 osteoarthritis between 2020 and 2023 were included. Propensity score matching balanced preoperative confounders, yielding 88 matched pairs (RA-TKA vs. CM-TKA). Outcomes included AKP intensity (Numeric Rating Scale, NRS), Knee Society Score (KSS), and active knee flexion/extension measured at 3, 6, 9, and 12 months postoperatively.

The RA-TKA group exhibited significantly lower AKP intensity at 3 months (17.5 ± 8.1 vs. 24.6 ± 10.7, p = 0.034), with no between-group differences thereafter. At 12 months, RA-TKA demonstrated superior KSS (41.5 ± 6.2 vs. 34.4 ± 5.6, p = 0.042), and knee flexion (110.3 ± 11.8° vs. 107.5 ± 12.5°, p = 0.044) and extension (3.6 ± 1.4° vs. 4.1 ± 1.5°, p = 0.020). AKP peaked at 3 months in both groups, with similar temporal trends postoperatively after surgery 6 months.

RA-TKA demonstrated better short-term improvement in both AKP and knee functional capacity compared to standard total knee arthroplasty, and the improvements of knee flexion and extension are significant advantages. Although RA-TKA showed comparable long-term outcomes in knee function and AKP risk assessment to conventional surgery, its clinical significance lies in the critical early postoperative period when over 80 % of AKP events occur within the first 3 months.