The Effect of Lower Limb Exoskeleton Alignment on Knee Rehabilitation Efficacy

Abstract

This study focuses on a musculoskeletal analysis of human lower extremity and associated muscle forces during different rehabilitative tasks and exoskeleton alignment models. By changing the size and orientation of the impairment levels that could be caused by the misalignment of the exoskeleton and biological knee joint, muscle stress variations were observed. This indicates an increase in force such as that generated by the Vastus lateralis muscle up to 4.3% due to a 5 mm lateral offset from an anatomically healthy knee joint location. In another setting, while a subject moved the shank through a circular trajectory using an exoskeleton support, muscle strain due to misalignment was reflected at the rectus femoris with a variation of 44%, the biceps femoris large head with 32% and the gastrocnemius muscles with 31–33% variation. These results suggest that misalignment should be taken into account while using exoskeletons with certain trajectories for knee rehabilitation purposes. Based on the shortcomings of conventional physiotherapeutic tasks, the outcome of this study can be helpful in prescribing an impactful yet convenient configuration toward a safe and promising rehabilitation process. Assessment of exoskeleton alignment during rehabilitation is important to ensure user safety with a better therapy efficacy.

Exploring Human–Exoskeleton Interaction Dynamics: An In-Depth Analysis of Knee Flexion–Extension Performance across Varied Robot Assistance–Resistance Configurations

“…A possible factor that may have contributed to the increase in the activation of the vastus medialis muscle in the modes using the robot is the misalignment of the exoskeleton and knee joint. This consideration is based on the work of [ 10 ] which observed an augmentation in muscle activations due to a misalignment between robot and human knee. Therefore, in future experiments, we intend to evaluate the issue of alignment between the joints of the robot and the subject.…”

“…A study to determine the effect of lower-extremity impairment due to exoskeleton knee joint misalignment during gait was conducted by [ 10 ]. Four levels of misalignment were designated to examine knee flexors and extensors.…”