A close look at how the ankle functions after a stroke could ultimately improve the mobility and rehabilitation outcomes for more than 40 million stroke survivors worldwide who experience persistent walking difficulties.

Supported by a $3.1 million grant from the National Institutes of Health, researchers at the University of Michigan will focus on how stroke affects the two fundamental properties of the ankle joint during human walking—and how a common medication may, or may not, help.

“Joint stiffness is a key factor in energy storage and forward movement, while joint viscosity describes resistance during gait,” said Elliott Rouse, professor of robotics and co-principal investigator of the project. “Unfortunately, these essential parameters are currently unaccounted for or misjudged in clinical settings.”

In addition to quantifying how these two properties affect how well people walk after experiencing a stroke, the team will develop a tool so that medical practitioners can easily measure them as well.

“Through this research, and by establishing a new tool to measure ankle properties in the clinic, we can advance our understanding, improve treatments and ultimately empower stroke survivors to regain mobility. This could enhance overall quality of life for millions of stroke survivors,” Rouse said.

Contrary to previous beliefs that ankle joint stiffness and viscosity both increase following a stroke, recent studies have revealed that these parameters remain unchanged or can even decrease compared to the unaffected side of the body. This misconception shows the need to investigate and understand the mechanics involved in order to develop more effective treatments.

One treatment in use now is botulinum neurotoxin (BoNT) injections, which are used to reduce joint stiffness. The team will study how they affect the properties of the ankle—and the implications for mobility.

Studying these mechanics is especially crucial because BoNT injections may further reduce ankle joint stiffness and viscosity, potentially hindering mobility.”

Chandramouli Krishnan, professor of physical medicine and rehabilitation, and co-principal investigator

“Our grant will not only investigate how ankle properties change after a stroke, but also assess the effects of BoNT injections and determine their impact on patient outcomes,” he said.

The research team includes Edward Claflin, an assistant professor of physical medicine and rehabilitation; James Richardson, a professor of physical medicine and rehabilitation; and Corey Powell, a statistician expert and adjunct professor of statistics.

“Our team is uniquely qualified to perform this research, as we have experts in biomedical and mechanical engineering, robotics, stroke rehabilitation, gait biomechanics and modeling, and clinician scientists, in addition to a world-class rehabilitation hospital,” Krishnan said.

The project is funded by NIH grant 1R01HD111567-01, Functional implications of stroke and Botulinum Neurotoxin on ankle stiffness and viscosity during gait.

Rouse is also an associate professor of mechanical engineering. Krishnan is also an associate professor of biomedical engineering and physical therapy, and an affiliate faculty member in robotics.