No Superiority of Total Knee Arthroplasty Alignment Philosophies: A Network Meta-Analysis Comparing Mechanical, Anatomical, Kinematic, Restricted Kinematic, and Functional Alignment Among Randomized Controlled Trials.

Abstract

Background: Although various total knee arthroplasty (TKA) philosophies exist, with different component and limb alignment targets, there is no consensus on which is superior. This study compared outcomes among randomized controlled trials (RCTs) of TKAs performed to achieve mechanical (MA), anatomical (AA), kinematic (KA), restricted KA (rKA), and functional alignment (FA).

Methods: Scopus, Ovid/MEDLINE, PubMed, Cochrane Database of Systematic Reviews, and Cochrane Central Registry of Controlled Trials were queried in April 2025 (PROSPERO: CRD420251017962). A frequentist model network meta-analysis of eligible prospective RCTs assessed complications, revisions, and patient-reported outcomes (PROs) using P-scores.

Results: Among 3,605 studies, 22 RCTs totaling 1,411 patients (1,428 primary TKAs) with median (interquartile range) age of 68.2 years (6.8) and follow-up of 29.1 months (48) were included for meta-analysis. The distribution of alignment philosophies was MA (n = 708, 49.6%), AA (n = 101, 7.1%), KA (n = 394, 27.6%), rKA (n = 160, 11.2%), or FA (n = 65, 4.6%). Compared to MA, the mean Knee Society Score (KSS) knee score improvements from baseline were statistically lower (worse) with AA (mean difference [MD] -0.503; 95% confidence interval [CI] -0.96 to -0.04; p = 0.0320) and KA (MD -0.623; 95% CI -1.07 to -0.18; p = 0.006), and mean KSS combined changes were also statistically lower (worse) with KA (MD -0.314; 95% CI -0.55 to -0.08; p = 0.009) versus MA. However, each statistically significant change had high heterogeneity and failed to reach the minimum clinically important difference. There were no significant changes in the mean Western Ontario and McMaster Universities Osteoarthritis Indices, KSS function, Oxford Knee, or Forgotten Joint scores among each alignment philosophy. In addition, postoperative knee flexion, complications, and reoperation rates with or without implant removal were similar among all techniques.

Conclusion: This study found no clinically meaningful difference in PROs nor complication rates among TKA alignment philosophies, supporting comparable short-term to mid-term outcomes. However, longer follow-up is required to accurately assess implant failure and revision rates.

Level of evidence: Therapeutic Level I. See Instructions for Authors for a complete description of levels of evidence.