  Assistive ankle-foot orthoses (AAFOs) are powerful solutions to assist or
rehabilitate gait on humans. Existing AAFO technologies include passive,
quasi-passive, and active principles to provide assistance to the users, and
their mechanical configuration and control depend on the eventual support they
aim for within the gait pattern. In this research we analyze the
state-of-the-art of AAFO and classify the different approaches into clusters,
describing their basis and working principles. Additionally, we reviewed the
purpose and experimental validation of the devices, providing the reader with a
better view of the technology readiness level. Finally, the reviewed designs,
limitations, and future steps in the field are summarized and discussed.
