Biomechanical predictors of primary ACL injury: A scoping review of prospective studies

Background

ACL injuries commonly occur in non-contact situations, particularly in sports involving jumping, landing, and cutting. Numerous biomechanical predictors for non-contact ACL injury have been proposed, yet existing reviews on biomechanical predictors vary in scope and findings.

Research question

This review aims to identify biomechanical predictors of primary ACL injury using a scoping review.

Methods

PubMed and EBSCO host (CINAHL Complete, MEDLINE Complete, SPORTDiscus) were searched from inception to March 1, 2023. Prospective studies that (1) examined discrete kinematic/kinetic variables during whole body movements (e.g., landing from a jump, cutting, and single-leg squatting) using 3D lab-based motion analysis, 2D video, or observational (non-instrumented) methods; and (2) produced a prediction model for the association between biomechanical variables (independent variable) and primary ACL injury (dependent variable) were included.

Results

11 studies were included. Jump-landing tasks were the most studied (9 studies), followed by change in direction (2 studies) and single-leg squatting (2 studies). Significant biomechanical predictors for non-contact ACL injury were reported in 7 studies during jump-landing/change in directions tasks. Kinematic predictors included decreased flexion (hip and knee) and increased knee valgus/internal rotation. Kinetic predictors included increased vertical ground reaction forces (landing/takeoff) and increased knee moments (valgus and knee extensor). Limited/conflicting evidence was found for all predictors. None of studies that employed 2D or observational methods (n=3) were able to identify predictors of ACL injury.

Significance

Biomechanical predictors of primary ACL injury were identified in 7 of 11 prospective studies included within this scoping review. The majority of the reported risk factors were identified using the drop jump, which was the most studied task (8 of 11 studies). The lack of standardization in biomechanical testing across studies limits the determination of specific predictive variables for primary ACL injury.