Development of a Six Bar Mechanism Based Active Knee Orthosis for Post-Stroke Gait Rehabilitation

An active knee orthosis can support a patient's weight and assist the knee during stance phase for improved gait assistance. This paper presents the development of a lightweight active knee orthosis (AKO) for post-stroke gait rehabilitation that is capable of providing assistive torque in a pattern that is similar to the natural pattern of the human leg. The proposed system is designed to be lightweight and comfortable to use. The system utilizes a single series elastic actuator and is controlled using the patient-driven motion reinforcement (PDMR) control to provide assistive torque to the user's knee based on the force information gathered from its series elastic link. A pilot study was performed with one young healthy subject wearing an ankle weight (4 kg) on one leg, in order to identify the effects and potential implications of using the AKO for gait assistance of hemiplegic subj ects. No discomfort was reported by the participant during the gait trials. Addition of the ankle weight reduced the knee movements, gait speed and gait balance, while increasing the knee range of motion asymmetry. While using the AKO, the subject was able to overcome much of the detrimental effects of the ankle weight and show improvements in majority of the outcome measures. Thus, the developed AKO exhibited promising outcomes in this pilot study that warrant further studies to better understand the implications of using this system during gait rehabilitation of stroke survivors.