###### Abstract  
Gait training for paraplegic patients is effective in preventing various complications due to prolonged sitting. In these patients, the use of powered exoskeletal-gait-orthosis (EGO) consumes lower energy than traditional training methods using non-powered EGO, such as a reciprocating-gait-orthosis (RGO). Thus, long-term training is possible and effective in increasing the activity level of the trunk muscles. However, more than 60% of paraplegic patients have incomplete injuries with residual function, which is inversely related to the functional role of the orthosis. We hypothesized that the gait ability in incomplete paraplegia could be improved by knee joint activation, and we developed a lightweight knee-actuated EGO (KAEGO). We verified its effectiveness in one patient with an incomplete spinal cord injury by comparing the metabolic cost of transport (COT) measured by a six minute walk test to a traditional non-powered EGO. We found that with increasing assist torque to the knee joint, the COT decreased by up to 24.5%, and the gait performance, including walking speed and travel distance, significantly improved up to 37% compared to that of the non-powered EGO. Future studies should verify the KAEGO system's effectiveness in a larger number of patients with various injury levels. exoskeletal gait orthosis; reciprocating gait orthosis; spinal cord injury +
Footnote †: journal:  
using an exoskeleton robot system appeared more efficient than Lokomat, which repeatedly trains a pre-defined joint trajectory on a treadmill [6]. Figure 1a shows fully powered exoskeleton robots such as the Exso, Rewalk, and HAL, which have been developed to assist daily life activities such as standing, walking, and climbing stairs in paralyzed patients. They are also classified as Class II medical devices by the U.S. Food and Drug Administration (FDA). However, in real-life environments, these robots are very unstable for climbing stairs and have limitations in their wearability because they are heavy and bulky [7]. Additionally, more than 60% of SCI patients are neurologically incomplete [8]. For such incomplete paraplegic patients with some residual muscles, the AAN (assist as needed) [9] approach may be useful. In particular, as the number of residual muscles increases, the functions to be assisted by the orthosis decreases, reducing the size of the exoskeletal gait orthosis (EGO) system [8]. Figure 1b shows an under-actuated exoskeleton system that supports loads and assists in walking using a kinetic energy storage function, and is mainly used to aid the user's power in industrial sites [9; 10]. Figure 1c shows the phoenix developed by [PERSON] [11] for gait rehabilitation. It has a hip-actuated-exoskeletal-gait orthosis (HAEGO), in which a motor assists only the hip joint, and a mechanical clutch is applied to the knee joint. It does not support higher functions such as climbing stairs, but basic movements, including sitting/standing/walking, are possible. Weighing 12.25 kg, it is lightweight and modular, with the advantage that the patients can wear it by themselves in a wheelchair. The human knee joint plays an important role in performing most daily activities, such as sitting, standing, and walking. In particular, when the range of the knee's motion is limited during walking, the patient's metabolic cost increases because unnatural movements such as hip elevation are accompanied by compensation [12]. [PERSON] et al. have reported that the foot swing acceleration of the active knee joint system is larger than that of the active hip joint system in the swing section after toe-off [13]. Based on these findings, the following two hypotheses were established. Firstly, by assisting the force that accelerates the body forward while walking through knee joint actuation, the user's metabolic cost can be reduced, and the walking speed can be improved.