Summary
Females may evoke sustained compressive loading force profiles over a smaller and more posterior portion of the tibiofemoral surface following ACL reconstruction.
Abstract
Background
Individuals with ACL injuries are at high risk for developing knee osteoarthritis (KOA) regardless of undergoing ACL reconstruction (ACLR) and rehabilitation. Aberrant gait biomechanics that persist after the completion of supervised rehabilitation contribute to KOA onset. ACLR patients are known to walk with less knee flexion range of motion and less dynamic compressive loading profiles during gait, characterized by lesser peak force but greater force across the limb during midstance. It is hypothesized that this aberrant gait profile leads to more sustained and focal loading of the articular tissues increasing the risk for KOA. Females exhibit a slightly higher overall risk of developing KOA in the general population; however, it remains unknown if a sex difference exists for gait biomechanics post-ACLR. Therefore, the purpose of this study was to compare compressive limb loading (i.e., vertical ground reaction force [vGRF]) and knee flexion angle (KFA) during gait between sexes at preoperative, 6 and 12 months post-ACLR time points.
Methods
Biological sex was recorded at the time of the initial preoperative clinic visit and gait biomechanics were collected over ground at a habitual walking speed using 3D motion capture at all three timepoints. vGRF and KFA were calculated throughout stance and time-normalized to 101 data points (0-100%) throughout stance phase. We conducted functional waveform analyses to evaluate percentages of stance phase that were different between males and females for vGRF and KFA.
Results
We included a total of 33 females (57%, age= 22.1±4.5 yrs, BMI= 23.5±3.0 kg/m2) and 25 males (43%, age= 21.4±4.9 yrs, BMI=25.0±3.3 kg/m2) in the study. There were no differences in vGRF between ACL injured females and males at any of the time points. Females demonstrated significantly greater KFA between 1 and 97% of stance at the preoperative timepoint, between 93 and 100% of stance at 6 months, and between 60 and 84% of stance at 12 months post-ACLR compared to males. As a confirmatory post hoc analysis, we evaluated if vGRF and KFA differed between ACLR individuals and uninjured controls for males and females, separately. As expected, we found that both ACLR females and males demonstrated components of a less dynamic vGRF waveforms (preoperative- lesser first and second peak and greater midstance; 6 months post-ACLR- lesser first peak and greater midstance, 12 months post-ACLR- lesser first peak) and less extended KFA during midstance at all 3 timepoints compared to their uninjured control female and male counterparts.
Conclusion
Both females and males demonstrate less dynamic, more sustained, compressive loading force profiles with more extended KFA during midstance compared to their uninjured counterparts. Overall, there were little differences between sexes for compressive loading, yet females demonstrated less extended knee during all of stance preoperatively, late stance at 6 and mid- to late stance at 12 months post-ACLR. These data suggest that females may evoke sustained compressive loading force profiles over a smaller and more posterior portion of the tibiofemoral surface that may specifically need to be addressed as part of sex-specific gait retraining intervention aimed at KOA prevention post-ACLR.