A team of student engineers at Worcester Polytechnic Institute (WPI) has developed a working prototype of a new type of sports shoe sole designed to reduce the incidence of non-contact knee and ankle injuries in organized sports. The shoe is a response to the large number of ankle and knee injuries—notably to the knee’s anterior cruciate ligament (ACL)—that plague amateur and professional athletes.
The WPI team is building, testing, and evaluating preliminary prototypes of the shoe in October and November. They hope to produce about 10 pairs in campus labs by January for further testing on the court. A larger trial production run is expected early in 2019.
According to the Journal of Athletic Training, the knee joint is the “…second most commonly injured body site after the ankle and the leading cause of sports-related injuries,” with more than 43,000 injuries occurring in high school athletes each year in a recent five-year period.
Researchers say the most common causes for ACL injury are landing from a jump, decelerating, and planting and pivoting off the foot.
The WPI shoe works by limiting loads to the ankle and knee, where many injuries occur. The key design element is a set of “goat’s-head springs”—tiny flexible polymer pieces whose name is a reference to WPI’s mascot. The springs are curled like goat’s horns, wrapping around posts that restrain, or localize, their deformation. The shoe recovers its initial configuration between steps, and the user may not notice that the shoe has responded to a potentially dangerous situation.
“The idea is that work from the effort exerted when someone is running and cutting would be absorbed by deforming the springs instead of tearing an ACL or spraining an ankle,” said Christopher Brown, professor of mechanical engineering, who is guiding the student team.