Functional versus mechanical alignment in robotic primary total knee arthroplasty: A meta-analysis

Functional alignment (FA) has emerged as a robot-enabled, patient-specific strategy in total knee arthroplasty (TKA), aiming to individualize component positioning and knee balance within predefined safety limits. However, whether robotic FA provides clinically meaningful advantages over robotic mechanical alignment (MA) remains uncertain. This meta-analysis compared robotic FA versus robotic MA in primary TKA.

Medline, the Cochrane Library, and Google Scholar were searched from inception to December 29, 2025, for comparative studies evaluating FA versus MA in robotic primary TKA. Outcomes included additional soft-tissue release, reported knee motion, Forgotten Joint Score-12 (FJS-12), 1-year functional score improvement using Oxford Knee Score or converted Western Ontario and McMaster Universities Osteoarthritis Index scores, and operative duration. Continuous outcomes were pooled as mean differences (MDs), and dichotomous outcomes as odds ratios (ORs).

Six studies including 645 TKAs were included. MA was associated with higher odds of requiring additional soft-tissue release compared with FA (OR = 5.38; 95% CI: 2.71 to 10.69; P < 0.00001). FA showed greater early improvement in reported knee motion at ≤6 weeks (MD = -4.64°; 95% CI: -7.07 to -2.21; P = 0.0002), but this difference was no longer significant at 6 months (MD = -1.13°; 95% CI: -8.24 to 5.98; P = 0.76). FJS-12 scores were similar at 3 months but favored FA at 6 months (MD = -10.74; 95% CI: -13.65 to -7.83; P < 0.00001), although this did not reach the established threshold for clinical importance. Functional score improvement at 1 year was similar between groups. Operative time statistically favored FA, although the difference was small.

Robotic FA was associated with fewer soft-tissue releases and greater early improvement in reported knee motion, but these early advantages did not translate into superior functional improvement by 1 year. Longer-term standardized comparative studies are required.