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

Abstract

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.

Keywords: anterior cruciate ligament (ACL); duty factor; external knee adduction moment (EKAM); gait asymmetry; knee flexion moment (KFM); post-traumatic osteoarthritis (PTOA).

Figure 1

Distribution curves for (a) EKAM (frontal plane) and (b) KFM (sagittal plane) knee joint moments (Nm/kg) amid the walking stance phase, taken from a single-sample trial. Positive and negative values signify (a) adduction and abduction and (b) knee flexion and extension moments, respectively. Each moment curve presents two calculated peaks, which are signified by crosses. Peak 1 (blue) and Peak 2 (green) represent the first and second halve of the stance phase, respectively. The time integral for each phase (1 and 2) of the respective curves (EKAM and KFM) were computed relative to time (Nm·ms/kg) when the knee moments (Nm/kg) were positive. Abbreviations: HS, heel-strike; FF, foot-flat; MS, mid-stance; HO, heel-off; TO, toe-off.

Figure 2

The sample mean distribution of ACL+ and ACL− groups for (a) gait asymmetry as a product of duty factor asymmetry (stance time/(stance time + swing time)), (b) EKAMp1 and (c) EKAMp2, (d) iEKAMp1 and (e) iEKAMp2, (f) KFMp1 and (g) KFMp2, and (h) iKFMp1 and (i) iKFMp2.* = p < 0.05, ** = p < 0.01 observed following am independent unpaired two-sample t-test.

Figure 3

A linear regression model displaying predictive relationships between the independent variable (x), gait asymmetry as a product of duty factor asymmetry (stance time/(stance time + swing time)) and independent variables (y) for (a) KFMp2 (R² = 0.665; p = < 0.001) and (b) iKFMp2 (R² = 0.505); p = < 0.001) in the ACL+ group.