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KnexFlex: Biofeedback for Rehabilitation Post ACL Injury

CSEF · 2026 Medicine & Physiology (Track 2) (Senior Division)

Andrew Metz

Overview

Rehabilitation following knee injury is commonly guided by intermittent clinical observation and subjective self-assessment, leaving a critical gap in objective, continuous feedback during everyday movement. As a result, compensatory gait patterns often develop and persist outside of clinical settings. This project presents KnexFlex, a wearable knee-angle tracking system developed as a instrument to investigate how the timing and structure of biomechanical feedback influence gait correction during injury recovery. The central hypothesis is that real-time joint-angle feedback functions as a closed-loop intervention capable of producing immediate improvements in gait mechanics and promoting short-term motor learning and lasting benefits. Seven healthy participants were evaluated to construct a normative baseline gait profile. Three individuals recovering from knee injuries were then assessed relative to this baseline using a novel similarity-based scoring framework ranging from 0 to 1000, where scores above 500 represent movement patterns within the average healthy range. 3 injured participants completed walking trials under two conditions: passive walking without feedback and active walking with real-time joint-angle feedback. Two patients also completed a follow-up testing session 8-12 hours later. The third, as time did not allow for the follow-up, completed a second full set of testing 2 weeks later. All injured participants demonstrated significant improvements in gait similarity scores during active feedback sessions and the two participants who were retested several hours later retained partial improvements despite the absence of feedback. These findings indicate that by reframing gait analysis as an interactive, closed-loop process, KnexFlex demonstrates the potential for accessible biomechanical feedback.

Competition history

  • CSEF 2026 Medicine & Physiology (Track 2) (Senior Division) · Entry S-21-09

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