# The Impact of COVID on Lower-Limb Exoskeleton Robotic System Patents--A Review
Rehabilitation of the lower limbs with the help of robotic exoskeletons appeared over 40 years ago as an alternative to conventional manual gait training [4,5]. These exoskeletal systems connect to the human body in a portable way. Compared to traditional therapy, walking rehabilitation using a robotic exoskeletal system can provide highly controlled training (being able to control the movement of all joints in the training and recovery process), repetitive and intensive [6], and can reduce the physical load on the therapist and provide accurate and fast progress of patients [7,8]. Among the latest patents applied for and published in 2021 (according to the Google Patents platform), it is registered in South Korea. It is entitled \"Lower extremity exoskeleton robotic device\" (Figure 1b). The patent application states that the present invention relates to a robot device with a lower exoskeleton used for rehabilitation exercises. The exoskeleton robotic system is a device mainly used for rehabilitation by supporting the muscular strength of the wearer when the lower extremities are paralyzed by accident or when the muscular strength of the lower extremities is insufficient due to old age. This device can also be used for industrial or military purposes, such as running [9]. Several revisions have emerged over the last decade that address various aspects of lower extremity rehabilitation and support devices. For example, in 2013, [PERSON] et al. [4] focused on robotic lower extremity care exoskeletons used in rehabilitation therapy. In 2015, [PERSON] et al. [10] presented a comprehensive analysis of all lower-limb exoskeletons developed after the 1990s; all devices analyzed were classified based on four criteria: mechanical structure, robot control system, user validation, and sensory devices used. Moreover, in 2015, [PERSON] et al. [11] analyzed the recent evolution of control mechanisms and strategies for robotic lower-limb rehabilitation devices. Then, in 2016, [PERSON] et al. [12] conducted a review of exoskeleton robots' construction and technological features for existing lower extremities, classifying them based on amplifying and rehabilitating human power into commercial or prototype versions. Moreover, in 2016, [PERSON] et al. [13] described the evolution of the exoskeletons of the lower limbs in terms of their structure, the control algorithms used, the detection technology to determine the wearer's intention to move, and the detection technology, the remaining challenges in this area. The walking rehabilitation exoskeletons presented in this review were classified as treadmill and ground training/assistance exoskeletons. Then, [PERSON] et al. [14] published a comprehensive study in 2019 summarising the current state of exoskeleton robots for lower limbs, focusing on human gait analy  
Figure 1: (a) US420179—Apparatus for facilitating walking, running and jumping (see the reference [1]); (b) KR102292983B1—Lower extremity exoskeleton robotic device (see the reference [9]). sis and the design of the drive system and control of these devices. Moreover, in 2019, [PERSON] et al. [15] analyzed 52 wearable exoskeletons of the lower limbs in their review, focusing on three main aspects of compliance: drive, structure, and interface attachment components. The authors highlighted the disadvantages and advantages of different solutions and suggested several promising lines of research. In 2021, [PERSON] and [PERSON] [16] conducted a review in which the primary purpose was to provide a comprehensive overview of the technological status of exosuits and the clinical results obtained when applied to users with reduced mobility based on 19 studies identified by the authors as relevant. Finally, in March 2022, [PERSON] et al. [17] published a study that provides a comprehensive review of how portable sensor technology has contributed to the activation and control of motorized ankle exoskeletons developed over the past two decades.