Lower Extremity Muscle Contributions to ACL Loading in Healthy and ACL-Reconstructed Females

Females are 16 times greater to sustain a second ACL injury compared to their healthy female counterparts. Many of these females return to play their respective sport after an ACL-reconstruction (ACLR). However, little is known about the influence fatigue in sport has on lower extremity mechanics of ACLR females. The purpose of this study was to investigate the influence muscular fatigue may have on lower extremity mechanics in healthy and ACLR females. It was hypothesized that 1) healthy control and ACLR females would demonstrate different hip, knee, and ankle mechanics, regardless of fatigue, 2) fatigue would influence hip, knee, and ankle mechanics, regardless of previous surgical intervention and 3) there would be an interaction between fatigue and previous surgical intervention. Seven healthy and four ACLR recreationally active females completed five anticipated land-and-cutting trials to the right pre- and post- a fatigue protocol. Three-dimensional lower extremity kinematic and kinetic variables were measured using a motion capture system and force plate. One-dimensional statistical non-parametric mapping were used to assess changes in lower extremity mechanics between healthy control and ACLR females over the entire stance phase. The only group ´ fatigue interaction found was hip flexion angle. Significant group main effects included hip flexion, abduction, and rotation angles. Significant fatigue main effects included hip flexion and knee abduction angles, as well as hip rotation moment. Hip and knee mechanics appear to be influenced by both fatigue and prior ACL surgery. However, hip mechanics seemed to be the most affected by prior ACL surgery, with fatigue being second. Therefore, future research is warranted to investigate the relationship between hip mechanics and ACLR.