Accurate restoration of native anterior cruciate ligament (ACL) orientation is a key goal of ACL reconstruction, yet MRI-based reference values remain inconsistent. This systematic review and meta-analysis aimed to define standardized native ACL sagittal (SIA) and coronal inclination angles (CIA) and compare them with the graft orientation achieved by contemporary reconstruction techniques.
MEDLINE, Embase, and Cochrane CENTRAL were systematically searched following PRISMA guidelines. Studies reporting MRI-based SIA and/or CIA using standardized tibial-axis–referenced measurements were included. Random-effects meta-analyses were performed to calculate pooled mean inclination angles with 95% confidence intervals (CIs).
Twenty-one studies including 2,047 knees were analyzed. The pooled mean native ACL SIA was 50.4° (95% CI 49.0°–52.0°), while the mean CIA was 67.5° (95% CI 63.3°–71.8°). Anteromedial portal and outside-in techniques most closely reproduced native ACL orientation, whereas transtibial reconstruction resulted in significantly greater sagittal graft inclination. No significant differences in coronal inclination were observed between techniques.
Standardized MRI-based reference values for native ACL inclination provide a robust anatomical benchmark for evaluating graft placement. Among current techniques, differences are primarily observed in sagittal graft orientation, highlighting its importance when assessing the anatomical accuracy of ACL reconstruction.