Purpose:​ The purpose of this study was to examine proximal tibial IMU accelerations between the involved limb and uninvolved limbs of individuals who have undergone ACL reconstruction performing the single-leg hop test battery and to correlate these results to deficits in quadriceps strength and distance hopped.

Methods:​ Thirty-four subjects (19 male, 15 female;​ age = 20.5 ± 6.7 years;​ mass = 76.4 ± 15.8 kg;​ height = 1.74 ± .08 cm) who have undergone unilateral ACL reconstruction were recruited for this study. An isokinetic dynamometer was used to assess the knee extension peak torque on the involved and uninvolved limbs. Two IMU sensors were placed on the tibial tuberosity of each limb and acceleration data were collected during the single-legged single and triple hop tasks. Seven acceleration variables were calculated in MATLAB including:​ Statistical analyses were preformed use SPSS statistical software. A two-factor ANOVA (subject, limb) was used to compare outcome variables and performance 150 milliseconds after landing during the single hop task. For the triple hop task, a three factor ANOVA (subject, limb, hop number) was used. Regression analyses were used to analyze the relationship between the asymmetry of the distance hopped and the asymmetries of the acceleration variables, and the asymmetry of the knee extension peak torque and the asymmetries of the acceleration variables

Results:​ Significant differences were found for most acceleration variables between the involved and uninvolved limbs during the single and triple hop tasks. However, no relationship was found between the asymmetry of the distance hopped or the asymmetry of the knee extension peak torque and the asymmetries of the acceleration variables.

Conclusion:​ This study aimed to examine the proximal tibial IMU accelerations between the involved and uninvolved limbs of individuals who have undergone ACL reconstruction. We also aimed to examine the relationship of the asymmetries of these acceleration variables and the asymmetries of the distance hopped during the functional hop tasks and the knee extension peak torque. Statistically significant differences were found in some variables between the involved and uninvolved limbs during the single and triple hop tasks. However, no correlation was found between the asymmetries of the acceleration variables and the asymmetry of the distance hopped or the asymmetry of the knee extension peak torque. These findings highlight the complexity of movement patterns in patients with ACLR and suggest that these acceleration measures may not consistently identify functional deficits across all individuals.