Review
Knee Exoskeletons Design Approaches to Boost Strength
Capability: A Review
Juan R. Meda-Gutiérrez
1
, Luis Adrián Zúñiga-Avilés
2,3,
* , Adriana H. Vilchis-González
1,2
and Juan Carlos Ávila-Vilchis
1,2
Citation: Meda-Gutiérrez, J.R.;
Zúñiga-Avilés, L.A.; Vilchis-González,
A.H.; Ávila-Vilchis, J.C. Knee
Exoskeletons Design Approaches to
Boost Strength Capability: A Review.
Appl. Sci. 2021, 11, 9990. https://
doi.org/10.3390/app11219990
Academic Editor: Hanatsu Nagano
Received: 6 September 2021
Accepted: 21 October 2021
Published: 26 October 2021
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1
Faculty of Engineering, Universidad Autónoma del Estado de México, Toluca 50130, Mexico;
jmedag001@alumno.uaemex.mx (J.R.M.-G.); avilchisg@uaemex.mx (A.H.V.-G.);
jcavilav@uaemex.mx (J.C.Á.-V.)
2
Faculty of Medicine, Universidad Autónoma del Estado de México, Toluca 50180, Mexico
3
Cátedras National Council on Science and Technology, Faculty of Engineering, Universidad Autónoma del
Estado de México, Toluca 50130, Mexico
* Correspondence: lazunigaa@uaemex.mx; Tel.: +52-5512018024
Abstract:
There are different devices to increase the strength capacity of people with walking
problems. These devices can be classified into exoskeletons, orthotics, and braces. This review
aims to identify the state of the art in the design of these medical devices, based on an analysis
of patents and literature. However, there are some difficulties in processing the records due to
the lack of filters and standardization in the names, generating discrepancies between the search
engines, among others. Concerning the patents, 74 patents were analyzed using search engines
such as Google Patents, Derwent, The Lens, Patentscope, and Espacenet over the past ten years. A
bibliometric analysis was performed using 63 scientific reports from Web of Science and The Lens
in the same period for scientific communications. The results show a trend to use the mechanical
design of exoskeletons based on articulated rigid structures and elements that provide force to move
the structure. These are generally two types: (a) elastic elements and (b) electromechanical elements.
The United States accounts for 32% of the technological patents reviewed. The results suggest that
the use of exoskeletons or orthoses customized to the users’ needs will continue to increase over
the years due to the worldwide growth in disability, particularly related to mobility difficulties and
technologies related to the combined use of springs and actuators.
Keywords: knee exoskeletons; lower limb exoskeleton; passive exoskeletons
1. Introduction
In recent decades, advances in the development of assistive devices have become
relevant in medicine, especially in specific areas related to people’s disabilities, increasing
its research and technological development. One of the main causes may be the worldwide
increase in the population that suffers from a disability. According to the World Health
Organization (WHO), more than 1000 million people live with some form of disability;
almost 200 million suffer considerable difficulties in their functioning. These mobility
difficulties are increased because of the aging of the population, and it will be a cause of
more significant global concern than it is now [1].
In this context, the prevalence of disability is increasing, and Mexico does not escape
this problem. According to data from the National Institute of Statistics and Geography
(INEGI), 7% of the population suffers from a disability, and 42.4% of disabilities are related
to mobility [
2
]. Another factor that affects the increase in the population with disabili-
ties is related to obesity. According to the Organization for Economic Cooperation and
Development (OECD) in its report “The Heavy Burden of Obesity: The Economics of
Prevention”, about 73% of the Mexican population suffers from overweight, and 34% of
people suffer from morbid obesity, which is the highest degree of obesity [
3
]. A great part
Appl. Sci. 2021, 11, 9990. https://doi.org/10.3390/app11219990 https://www.mdpi.com/journal/applsci
