Review of Nine 1DOF-Actuated Knee Exoskeletons for ACL Injuries

Exoskeleton is one of the advanced strategies to assist knee injury patients to regain their mobility without experiencing as many risks and pains compared to the usage of traditional equipment such as cane and crutches. Knee injuries, such as Anterior Cruciate Ligament (ACL) injuries, disable a person’s leg to flex and extend to a certain degree, depending on the degree of injury. For Grade 1 and Grade 2 ACL injuries, a knee exoskeleton can be introduced. The knee exoskeleton can reduce the patient’s moving effort by providing extra torque to the flexion and extension of the leg, a.k.a. 1DOF actuation. This study has reviewed nine (9) knee exoskeletons in terms of their mechanism design, functions, and feasibility. Each exoskeleton displayed its design advantages as well as shortcomings. Many exoskeletons’ creators do not disclose their technical specifications for some reason. The author has provided reviews and recommendations based on the available but limited online information, mainly from research journal articles, review articles and brief mentions in the sources above. Depending on the design layout, all exoskeletons are particularly useful for rehabilitating ACL injury patients within the hospital’s treatment room and for some exoskeletons, beyond the hospital area. These exoskeletons are utilizing a variety of compliant mechanisms to facilitate their movements. Finally, a compilation of desirable characteristics of a knee exoskeleton is provided at the end of this paper. While most of other literature focus on technical characteristics from the inventor’s (manufacturer) perspective, this study focuses on a mix of characteristics where the patient’s (consumer) perspective is also considered.