A Proprioceptive Training Program Using an Uneven Terrain Treadmill for Patients With Ankle Instability

Inclusion Criteria 1. Aged 18-49. 2. Score \< 24 on the Cumberland Ankle Instability Tool. 3. Foot and Ankle Ability Measure Activities of Daily Living score ≤ 90 and Sports score ≤ 80 indicating substantial ankle-foot impairment and activity limitation. 4. Able to attend treatment sessions for approximately a 6-week period. 5. Passed most recent physical fitness test (Active duty only). 6. Acute lateral ankle sprain specific inclusion criteria: 1. history of a first-time ankle sprain that resulted in activity limitation that lasted at least one day. 2. chronicity of 2-6 weeks prior to consent. 7. Chronic ankle instability specific inclusion criteria: 1. history of at least one significant ankle sprain within the 12 months prior to enrollment that interrupted physical activity for 1+ days. 2. most recent ankle sprain in the past 2-12 weeks. 3. history of the previously injured ankle joint "giving way" and/or recurrent sprain and/or ''feelings of instability.'' 8. Individual is about to start care with physical therapy. Exclusion Criteria 1. Unable to walk at the point of study enrollment. 2. Non-removable casting. 3. History of previous surgeries to the musculoskeletal structures (i.e., bones, joint structures, nerves). 4. History of fracture in either limb of the lower extremity requiring realignment. 5. Acute injury to musculoskeletal structures of other joints of the lower extremity within the previous three months, which impacted joint integrity and function resulting in at least one interrupted day of physical activity. 6. Pregnant. 7. Self-reported disability due to neuromuscular impairment in the lower extremity, neurological or vestibular impairment that affected balance. 8. Connective tissue disorder (e.g. Marfan Syndrome or Ehlers-Danlos syndrome). 9. Anyone separating from the military within 12 months (other than normal military retirement), pending a medical evaluation board, discharge from the military for medical reasons, or pending or undergoing any litigation for an injury.