Proprioceptive afferents from the ankle joint are essential feedback for maintaining balance. However, there is no widely accepted test or measurement system available for determining the proprioceptive accuracy of the human ankle joint. Here, we present a system with a novel hardware design that applies an established psychometric testing protocol that generates a Just-Noticeable-Difference (JND) threshold as a measure of ankle proprioceptive acuity at the end of testing. To establish the system validity, twelve healthy adult participants completed the assessment. Testing required 25 trials and took approximately 10 minutes to complete. We show exemplar data of the ankle JND threshold and the summary results for all twelve participants. This assessment has the potential to become a tool for clinicians to identify proprioceptive impairment at the ankle and to assess the efficacy of sensorimotor interventions for improving balance in clinical populations.