The Knee Anterolateral Ligament is Present in 82% of North American and 65% of European But Only in 46% of Asian Studies: A Systematic Review of Frequency and Anatomy.

Purpose: To perform an updated systematic review on the prevalence and morphological characteristics of the anterolateral ligament (ALL) in human cadaveric specimens.

Methods: Medline, Embase, Scopus, and Google Scholar were searched for studies from 2012 to 2024 describing the morphology. Study quality was assessed using CASP checklist and QUACS scale. Heterogeneity was analysed with the I² statistic, funnel plot, and Q-test. Mean effect size and 95% prediction intervals were calculated. Prevalence and anatomical measurements (length, width, thickness) were analysed using mean and standard deviations.

Results: Thirty studies were included. CASP identified three low-quality studies. Twelve studies met the QUACS quality threshold. The prevalence of the ALL was 61.7% (82% North America, 64.9% Europe, 45.8% Asia). The femoral insertion showed variability near the lateral femoral epicondyle and lateral collateral ligament, while the tibial insertion was midway between Gerdy's tubercle and fibular head. Histological analysis revealed 60% of studies identified ligamentous tissue similar to the ACL. The mean ALL length was 39.7 mm, width 5.5 mm, and thickness 1.5 mm, with no significant morphological differences among populations.

Conclusion: This systematic review reveals that the ALL is present in 61.7%, with prevalence rates of 82% in North American studies, 65% in European studies, and 46% in Asian studies. The femoral insertion exhibited substantial variability at/around the lateral femoral epicondyle and LCL, lacking consistency. The tibial insertion was more consistently described as being located about halfway between Gerdy's tubercle and the fibular head. Histological analysis showed that 60% of the included studies identified the ALL as containing ligament-like or ligamentous tissue. The mean length of the ALL was 39.9 mm (range 31-59 mm), the mean width was 5.7 mm (range 2.2-9.0 mm), and the mean thickness was 1.5 mm (range 1.3-2.7 mm). No significant ethnic population differences were observed in the morphological measures.