500 Section - The metabolic cost and mechanics of walking with a spring-loaded stabilizing knee device: a curious case of an individual living with post-polio syndrome

Wednesday, May 20, 2026

6:00 PM - 7:30 PM PT

Presenting Author/Autor expositor(s)

CA

Christopher J. Arellano, PhD

Associate Professor
Dept. of Orthopedic Surgery and Dept. of Biomedical Engineering, University of Arizona
Tucson, Arizona, United States

Co-Author/Coautor(s)

EM

Everett J. Moore, n/a

Undergraduate Student
University of Arizona
Bainbridge Island, Washington, United States
AC

Andrew Carlson, n/a

Undergraduate Student
University of Arizona
Maple Grove, Minnesota, United States
FE

Francisco Espinoza, MS

PhD student
University of Arizona
Tucson, Arizona, United States
KH

Kavan Hazeli, PhD

Associate Professor
University of Arizona
Tucson, Arizona, United States

Case Diagnosis: We report a case study on the use of spring-loaded spring stabilization (SLS) knee device developed for an individual living with post-polio syndrome. During the span of 2-13 years of age, the disease caused muscle-tendon degeneration, causing lower limb skeletal deformities that left his legs in crossed and flexed position. After several reconstructive surgeries that straightened his legs, he eventually received physical therapy and gait rehabilitation training at 15 years of age. After two years, he learned to walk using forearm crutches, but till this day (age 36, mass = 45 kg, height = 152 cm), he still relies on forearm crutches because of significant weakness of his right leg.

Case Description: Thus, our goal was to reduce his risk of falling and feeling of exhaustion by improving his right limb function so as to reduce his walking net metabolic cost. We developed a custom knee brace that integrated stabilizing hinges that prevented hyperextension but allowed for limited knee flexion. In addition, we were also inspired by the role that biological spring-like tendons play during human walking. Therefore, to mimic the function of the quadriceps muscle-tendon unit, we positioned rubber springs in front of the knee which allowed for significant energy storage and return.

Discussions: We discovered that across slow to modest walking speeds (0.1-0.5 m/s), his net metabolic cost of transport (COT) ranged from 28-10 J/kg/m, which is amongst the highest that has ever been reported for a human walking on two legs. We also discovered that walking with the SLS knee device improved his net COT by ~25%, which is explained by its stabilizing and spring-like behavior that facilitated swing leg.

Conclusions: The benefits of the SLS knee device are promising and our current work is focused on optimizing the mechanical behavior of the springs, which could further promote walking improvements.