Characterizing knee loading asymmetry in individuals following anterior cruciate ligament reconstruction using inertial sensors

- Difficulty identifying knee loading deficit may underline their persistence.
- Altered knee loading is related to altered heel rocker mechanics during gait.
- Shank angular velocity plays an important role in calculating knee extensor moment.
- Angular velocity between-limb ratios predict knee extensor moment deficits.
- Wearable sensor gyroscopes detect gait impairments following ACL reconstruction.

Limitations in the ability to identify knee extensor loading deficits during gait in individuals following anterior cruciate ligament reconstruction (ACLr) may underlie their persistence. A recent study suggested that shank angular velocity, directly output from inertial sensors, differed during gait between individuals post-ACLr and controls. However, it is not clear if this kinematic variable relates to knee moments calculated using joint kinematics and ground reaction forces. Heel rocker mechanics during loading response of gait, characterized by rapid shank rotation, require knee extensor control. Measures of shank angular velocity may be reflective of knee moments. This study investigated the relationship between shank angular velocity and knee extensor moment during gait in individuals (n = 19) 96.7 ± 16.8 days post-ACLr. Gait was assessed concurrently using inertial sensors and a marker-based motion system with force platforms. Peak shank angular velocity and knee extensor moment were strongly correlated (r = 0.75, p < 0.001) and between limb ratios of angular velocity predicted between limb ratios of extensor moment (r2 = 0.57, p < 0.001) in the absence of between limb differences in spatiotemporal gait parameters. The strength of these relationships indicate that shank kinematic data offer meaningful information regarding knee loading and provide a potential alternative to full motion analysis systems for identification of altered knee loading following ACLr.