Effect of Static Alignment on Dynamic Knee Abduction Moments in Adolescent Athletes with Recent ACL Reconstruction

Stepping into a safer movement: The relationship between foot progression angle and lower extremity biomechanics during a 45-degree run-cut maneuver

BACKGROUND

Anterior cruciate ligament injury rates are high and often associated with change-of-direction movements. Analysis of youth movement patterns is critical for avoiding injury and foot progression angle affects lower extremity kinematics during cutting movements. Knee abduction and hip adduction are known predictors of anterior cruciate ligament injury. The relationship between foot progression angle and lower extremity biomechanics lacks exploration in youth athletes following anterior cruciate ligament reconstruction. This study aimed to assess the relationship between foot progression angle at max knee flexion, and mechanics predictive of anterior cruciate ligament injury during a change-of-direction task in youth athletes following anterior cruciate ligament reconstruction.

METHODS

Thirty-four participants (12 m, 15.0 ± 2.5 years) who previously underwent anterior cruciate ligament reconstruction participated in the study. Participants performed a 45-degree run cut task on both affected and unaffected limbs. Trunk and lower extremity biomechanics were collected using 3D motion capture and force plates.

FINDINGS

Moderate correlations were observed on the affected limb for trunk, pelvis, hip, knee, and ankle angles, as well as ankle moments (r = -0.34-0.52). On the unaffected limb, moderate correlations were seen in pelvis, hip, and ankle angles (r = 0.41-0.44). Significant differences exist between limbs for pelvis, hip and knee angles, as well as knee moments (p ≤ 0.038).

INTERPRETATION

Youth athletes appear to exhibit cutting movement patterns following anterior cruciate ligament reconstruction that may increase their risk of anterior cruciate ligament reinjury. Foot progression angle is a potential component of cutting tasks that clinicians and coaches can use to reduce an athlete's injury risk.

Relationship of Knee Abduction Moment to Trunk and Lower Extremity Segment Acceleration during Sport-Specific Movements

The knee abduction moment (KAM) has been identified as a significant predictor of anterior cruciate ligament (ACL) injury risk; however, the cost and time demands associated with collecting three-dimensional (3D) kinetic data have prompted the need for alternative solutions. Wearable inertial measurement units (IMUs) have been explored as a potential solution for quantitative on-field assessment of injury risk. Most previous work has focused on angular velocity data, which are highly susceptible to bias and noise relative to acceleration data. The purpose of this pilot study was to assess the relationship between KAM and body segment acceleration during sport-specific movements. Three functional tasks were selected to analyze peak KAM using optical motion capture and force plates as well as peak triaxial segment accelerations using IMUs. Moderate correlations with peak KAM were observed for peak shank acceleration during single-leg hop; peak trunk, thigh, and shank accelerations during a deceleration task; and peak trunk, pelvis, and shank accelerations during a 45° cut. These findings provide preliminary support for the use of wearable IMUs to identify peak KAM during athletic tasks.