Functional alignment versus mechanical alignment in total knee arthroplasty: a meta-analysis of randomized controlled trials

Functional alignment (FA) is a recently developed personalized alignment technique designed to optimize implant positioning by preserving the soft tissue envelope and restoring the joint line and articulation according to the surrounding soft tissue. This meta-analysis evaluated the clinical efficacy of FA compared with mechanical alignment (MA) in total knee arthroplasty (TKA). A systematic search of PubMed, Embase, Web of Science, and the Cochrane Library was conducted for randomized controlled trials (RCTs) published up to August 14, 2025. Random-effects models were used for all pooled analyses, and the certainty of evidence for each outcome was assessed using the GRADE approach. Four RCTs met the inclusion criteria. Pooled analyses showed that the Forgotten Joint Score (FJS) was statistically higher in the FA group than in the MA group; however, the magnitude of the difference did not reach previously reported thresholds for a clinically important change. FA was also associated with a significantly different lateral distal femoral angle (LDFA) and higher postoperative patient satisfaction. However, no statistically significant differences were observed between the two groups in flexion range of motion (ROM), Oxford Knee Score (OKS), visual analog scale (VAS), rest pain, EuroQol 5 Dimensions (EQ-5D) VAS, or medial proximal tibial angle (MPTA). These findings suggest that FA may be associated with modest improvements in some patient-reported outcomes; however, the observed FJS difference may not represent a clinically perceptible benefit, and the certainty of evidence ranged from low to moderate.