Exoskeletons are becoming powerful tools to support therapists during rehabilitation and assist patients with locomotion difficulties. Most of the exoskeletons in the literature (Sanz-Morere et al. 2019), (Giovacchini et al. 2015) are based on a hierarchical control structure: (i) a high-level controller that estimates the user’s locomotion intent, (ii) a mid-level controller that implements an adaptive assistive strategy, and (iii) a low-level controller that manages the actuation units. This work aims at designing and validating a high-level classification algorithm for a portable active knee orthosis (AKO), previously developed by the team of engineers of the Wearable Robotics Lab, at The BioRobotics Institute (Scuola Superiore Sant’Anna, Pisa).