Genu recurvatum is one of the common problems in patients with hemiplegia after stroke. For its improvement, it may be important to manipulate the ankle movement in coordination with the knee during gait. However, no device is available yet that can achieve it. We are developing a new exoskeleton robot that can assist knee and ankle joints simultaneously. This study aimed to test the feasibility of the robot in healthy individuals and patients with stroke, and to investigate its effect on genu recurvatum during gait.

Two healthy individuals and two patients with chronic stroke participated in this study. Healthy individuals received the robot-assisted gait training for 60min in total. We assessed the safety of the training and muscle activities during gait with or without the robot-assistance. Patients with stroke had moderate lower-limb paralysis and genu recurvatum during gait. They received the robot-assisted gait training for 30min in total. The robot consisted of a knee ankle foot orthosis and an actuator with pneumatic artificial muscles (Fig. 1). We adjusted the assist parameters to prevent their knee hyper-extension during the stance phase. We evaluated the range of knee joint motion, temporal and spatial parameters during over-ground gait without the robot before and after the intervention.

All participants safely completed the training. The robot decreased muscle activities during gait in healthy individuals. One of the patients showed a decrease in the maximum knee extension range during the stance phase, an increase in the maximum knee flexion range during the swing phase, and improvements in the temporal and spatial asymmetries.

The robot which can assist knee and ankle joints simultaneously has a potential to be a new therapeutic device for genu recurvatum in patients with hemiparetic stroke.