# Footnote 1
## 1 Introduction  
Below-knee amputation (BKA) is a surgical procedure that mainly originates from trauma, diabetes, and peripheral vascular diseases [1]. While it is estimated that an average person walks about 6500 steps per day, current trends suggest that 10,000 steps per day represent a healthy lifestyle [2] for which a suitable prosthesis is necessary for a BKA patient in order to achieve a complete user reintegration to his/her pre-amputation activities. These designs should adapt to different patient's activities.  
In scientific documents, there is wide confusion with the terms prosthesis, prosthetic, and prostheses; prosthetic is the process to manufacture an artificial member (AM), prosthesis a component of the AM, and prostheses are all the components that make up an AM. From patents and scientific document searches, the term prosthesis is more commonly used; in this paper, prostheses and prosthesis will be used interchangeably.  
Understanding the functioning of these prostheses is necessary to identify the foot movements: internal-external axial rotation,eversion-inversion, dorsiflexion (DF), and plantar flexion (PF), as shown in Figure 1. The forces acting on the human foot are distributed with 60% towards the heel and 40% towards the phalanges. The loads are distributed between the heel and the metastasis to the fourth and fifth phalanges and towards the big to be to the second and third phalanges [3].  
In order to improve and develop ankle/foot prostheses, it is necessary to know and understand present-day solutions to walking and running for BKA patients (and the people behind those solutions), so our designs meet both user and technical requirements. A state-of-the-art analysis of BKA prostheses is performed in this research.  
Foot prostheses can be classified as follows:  
* Ankle-cushion heel (SACH-foot): This was developed in the 1950s and incorporated a compressible heel that dampens the impact on the ground while emulating a plantar flexion movement. This type of prosthesis is used for its relatively low cost and weight [4].
* ESAR, also known as ESR, was developed in the 1980s. This type of prosthesis uses a foot-modeled plate (usually carbon fiber made) that stores elastic potential energy and progressively releases it as kinetic energy [5].
* CESR prostheses aim to capture the energy that is dissipated during a gait impact. On the loading phase of stance, energy is stored by a spring and locked. Then, this energy is timely released during the terminal stance of walking using microelectronic components [5].
* Active prostheses are considered state-of-the-art prostheses due to the use of actuators, microcontrollers, or other electronic devices; usually, these work using ESAR foot systems combined with some external elements such as actuators or other electronic components. These prostheses have better control and stability during a walk cycle [6].  
In the next section, it is explained how the investigation was performed for both patents and scientific communications. The Result Section presents a discussion about a new prosthesis classification according to this investigation, main authors, countries, and keywords analyzed. In the discussion Section, findings and other designs of prosthesis designs are disclosed.