# Gait Asymmetry and Post-Traumatic Osteoarthritis Following Anterior Cruciate Ligament Rupture: A Preliminary Study

## TL;DR

This study suggests that gait asymmetry after ACL injuries may contribute to early knee osteoarthritis in younger adults.

## Contribution

The study is among the first to explore gait asymmetry's role in early post-traumatic osteoarthritis following ACL ruptures.

## Key findings

- Participants with ACL injuries showed greater gait asymmetry and joint loading compared to those without injuries.
- Duty factor asymmetry was strongly correlated with increased knee flexion moments, suggesting a link to PTOA progression.
- The findings imply that gait asymmetry may play a role in early-stage PTOA development following ACL tears.

## Abstract

Knee post-traumatic osteoarthritis (PTOA) is a type of osteoarthritis (OA), typically occurring in younger adults following serious joint injuries such as anterior cruciate ligament (ACL) tears. Walking gait asymmetry, whereby a person favours one leg over the other, leads to abnormal joint loading, which can drive the development of OA and PTOA and can cause chronic joint degeneration. Gait asymmetry-induced joint loading worsens late-stage OA severity; however, early-stage involvement and treatments, particularly in PTOA, are poorly defined. This research explored the involvement of gait asymmetry in early-stage PTOA following ACL tears in younger adults. Participants with historical ACL tears (ACL+) and participants with no previous joint trauma (ACL−) underwent gait analysis, determining gait asymmetry and abnormal joint loading severity. Our work found that gait asymmetry and joint load were greater in participants with previous ACL injuries, and gait asymmetry was seen to potentially cause increased knee flexion moments, a common joint load metric. Therefore, these preliminary data imply that gait asymmetry-induced joint loading may contribute to early-stage PTOA in subjects with ACL tears. This study was exploratory, and more research is required to validate and reinforce these findings before prospective treatments can be developed.

Knee post-traumatic osteoarthritis (PTOA) often develops in younger populations following anterior cruciate ligament (ACL) rupture, accounting for 12% of all symptomatic osteoarthritis (OA). The current literature implicates gait asymmetry in late-stage knee OA progression; however, early-knee PTOA development involvement is ill defined. This study explored gait asymmetry involvement in early-stage knee PTOA following ACL ruptures. Gait asymmetry, measured as asymmetry in duty factor (relative contact time), and joint loading data were collected, using infrared-camera motion capture and Kistler force plates for participants exhibiting either historical ACL ruptures (ACL+; n = 4) or no previous joint trauma (ACL−; n = 11). Joint loading measures included external knee adduction moment (EKAM) and external knee flexion moment (KFM), early (peak 1; EKAMp1 and KFMp1) and late (peak 2; EKAMp2 and KFMp2), stance peaks (Nm/kg), and respective time integrals (Nm·ms/kg; iEKAMp1, iEKAMp2, iKFMp1, and iKFMp2). ACL+ exhibited greater asymmetrical duty factor (78% difference) and greater joint load differences: EKAMp1 (26%), EKAMp2 (49%), KFMp1 (37%), iKFMp1 (44%), and iKFMp2 (60%). Significant relationships were found between duty factor asymmetry and both KFMp2 (R2 = 0.665) and iKFMp2 (R2 = 0.504). These preliminary data suggest gait asymmetry-induced joint loading may contribute to knee PTOA progression, but further research with increased sample sizes and the quantitative assessment of cartilage status is required.