Relationship of knee abduction moment to lower extremity segment accelerations during sport-specific movements in youth anterior cruciate ligament reconstruction patients at return-to-play

Background: Second injury rates after anterior cruciate ligament reconstruction are high, necessitating tools to identify injury risk factors prior to return to sport. Knee abduction moments are a predictor of anterior cruciate ligament injury but require access to a motion laboratory to collect, thus reducing clinical feasibility. Inertial measurement units have been explored as an efficient, lower cost solution. However, the relationship between linear acceleration, derived from inertial measurement units, and knee abduction moments have not been explored in youth athletes after anterior cruciate ligament reconstruction. Therefore, the purpose of this study is to assess the relationship between lower extremity segment acceleration, derived from wireless inertial measurement units, and knee abduction moment during athletic tasks in youth athletes after anterior cruciate ligament reconstruction. Methods: Thirty-four participants (12 male, 15.0 +/- 2.5 years) who were 10.1 +/- 1.9 months post-anterior cruciate ligament reconstruction participated in the study. Participants performed a single leg hop, a run plant, and a 45 degrees run cut task. Peak knee abduction moment was collected using optical motion capture and force plates while peak triaxial acceleration was collected for the lower extremity using inertial measurement units. Findings: Moderate correlations were observed for thigh and shank linear acceleration and knee abduction moment across all athletic tasks. Observed differences in linear acceleration between limbs were also identified. Interpretation: These findings support the use of linear acceleration, derived from wireless inertial measurement units, to supplement detection strategies of high knee abduction moment during athletic tasks in youth athletes after anterior cruciate ligament reconstruction.