Knee Morphometry in Asian and Western Populations: A Systematic Review and Meta-Analysis of Anterior Cruciate Ligament-Related Parameters.

IMPORTANCE: Intercondylar notch dimensions, anterior cruciate ligament (ACL) width, and posterior tibial slope (PTS) are recognized as important anatomical factors associated with ACL injury risk, and anatomical reference values for these parameters are derived predominantly from Western cohorts. Individual studies suggest that ACL-related knee morphology may vary across populations, but whether such differences are consistent between Asian and Western populations across commonly assessed magnetic resonance imaging (MRI)-measured parameters remains uncertain. AIM: To determine whether MRI-measured knee morphology differs between geographically defined Asian and Western adult populations with radiologically intact ACLs across six prespecified parameters: femoral notch volume (FNV), notch width (NW), notch width index (NWI), medial tibial slope (MTS), lateral tibial slope (LTS), and ACL width. METHODS: This systematic review and meta-analysis was conducted according to the Preferred Reporting Items for Systematic Reviews and Meta-Analyses (PRISMA) 2020 statement and prospectively registered with the International Prospective Register of Systematic Reviews (PROSPERO) [CRD420261403854]. Four electronic databases were searched from inception to 11 June 2026 for MRI studies reporting eligible morphometric outcomes in adults with radiologically intact ACLs. Studies were classified as Asian or Western by country of cohort recruitment, reflecting geographic origin rather than verified individual ethnicity. Single-arm random-effects meta-analyses using restricted maximum likelihood estimation were pooled separately by cohort and compared using the Q test for subgroup differences. Meta-regression evaluated geographic cohort, measurement technique, mean age and sex composition as potential sources of between-study variation. Statistical significance was defined as two-sided p < 0.05. CONCLUSION: MRI measures of femoral notch morphology, PTS, and ACL width did not differ statistically significantly between Asian and Western populations with radiologically intact ACLs (p = 0.08-0.78). Given the substantial heterogeneity and wide prediction intervals, these findings indicate an absence of detectable differences in the available literature rather than anatomical equivalence between populations, and clinically important differences cannot be excluded. Clinically, geographic origin alone should therefore not be considered a surrogate for individual knee morphology when assessing ACL-related anatomical risk or planning reconstruction. Although study-level sex composition, mean age and measurement technique may contribute to variation in the measured parameters, these associations should be interpreted cautiously given the ecological nature of the analysis. LEVEL OF EVIDENCE: Level IV (systematic review and meta-analysis of Level III-IV observational studies).