Date of Award


Document Type


Degree Name

Doctor of Philosophy (PhD)


Biomedical Engineering



Research Advisor

Denis J. DiAngelo


Eugene C. Eckstein; Richard J. Kasser; William M. Mihalko; Maxime R. Paquette; Douglas W. Powell


Foot and Ankle, Functional, Gait, Mechanical Pain, Orthosis


Over two million Americans visit the doctor each year for foot and ankle pain stemming from a degenerative condition or injury. Standard of care ankle-foot orthoses have been shown to effectively manage pain symptoms of the lower limb, but they can also significantly hinder joint motion and limit function. The Dynamic Ankle Orthosis (DAO) was created with the intent to alleviate pain using an offloading mechanism without interfering with natural joint motion. This dissertation presents the development, benchtop validation, functional assessment, and clinical evaluation of this novel treatment option for patients suffering from acute and chronic foot and ankle pain.A benchtop validation study was performed to determine the offloading capacity of the DAO during static double stance and to quantify the brace’s effect on passive ankle motion. Static offloading of the DAO was measured using load cells, and an isokinetic dynamometer measured resistance to passive, non-weight-bearing ankle motion with and without the brace. The DAO offloaded between 11%-30% BW with 77%-95% brace force transference. The DAO permitted a functional range of ankle motion (10° dorsiflexion to 20° plantarflexion) and did not increase resistance to ankle motion.In a gait laboratory setting, a functional assessment was performed with ten healthy subjects to compare ankle joint kinematics and plantar pressures during treadmill walking among the DAO, a standard double upright ankle-foot orthosis (DUAFO), and an unbraced control (CON) condition. Ankle kinematics were assessed using a 3D motion capture system and in-shoe plantar pressures were measured for seven areas of the foot. DAO reduced hallux peak plantar pressures compared to CON and DUAFO. Peak plantar pressures under toes 2-5 were smaller in DAO than DUAFO. Eversion ROM was much smaller in DUAFO compared to CON and DAO. The impact of the DAO on pain and function was evaluated in a clinical setting with twenty-five patients symptomatic with foot and/or ankle pain. Eight functional activities were completed with CON and DAO. Force insoles were used to capture in-shoe vertical forces and a visual analog scale was used to assess pain levels during each activity. A post-test questionnaire was used to measure the self-perceived impact of the DAO on the patient’s symptoms and function. Peak in-shoe forces were reduced during level and stair walking (p<0.05). Average pain was 1.2 to 1.6 points lower with DAO than CON for the active tasks (clinically meaningful). Most participants reported that the DAO either improved (n=19) or did not affect their symptoms (n=5). Function scores were improved on average (+3.7). DAO improved symptoms of osteoarthritis, posterior tibialis tendon dysfunction, postoperative pain, ankle sprains, and nerve disorders. This body of work demonstrates the capacity of the DAO to provide significant offloading during ambulation without greatly affecting kinematic parameters including sagittal and frontal plane ankle motion compared to an unbraced control. Additionally, this work provides novel evidence that the DAO can improve symptoms and the ability of impaired individuals to complete functional activities such as level and stair walking.




2020-008-Chung-DOA.pdf (423 kB)
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