QUESTIONS: Is loss of proprioception or loss of motor control related to functional ankle instability? Are proprioception and motor control related? Is there any difference in proprioception or motor control between ankles with different severity of functional ankle instability? DESIGN: Cross-sectional, observational study. PARTICIPANTS: Twenty people aged between 18 and 40 years with functional ankle instability associated with a history of ankle sprain more than one month prior. Twenty age-matched controls with no functional ankle instability or history of ankle sprain. OUTCOME MEASURES: Functional ankle instability was classified using the Cumberland Ankle Instability Tool, proprioception at the ankle was measured as movement detection at three velocities, and motor control was measured using the Landing Test and the Hopping Test. RESULTS: There was little if any relation between proprioception (r = 0.14 to 0.03, 95% CI 0.40 to 0.25) or motor control (r = 0.08 to 0.07, 95% CI 0.35 to 0.20) and functional ankle instability. There was also little if any relation between proprioception and motor control except for a low correlation between movement detection at 0.1 deg/s and the Landing Test (r = 0.35, 95% CI 0.09 to 0.58). Furthermore, there was no difference between the ankles with or without functional ankle instability in proprioception or motor control. CONCLUSION: By greater than one month after ankle sprain, loss of proprioception does not make a major contribution to functional ankle instability.