NRL’s Edison Program Funds Study into Knee Joint Brace Efficacy

With its large staff of doctoral students and lab employees, the U.S. Naval Research Laboratory is an ideal setting for grooming the nation’s future science leaders.

NRL’s Edison Program provides an avenue through which these high achieving employees can pursue graduate studies related to their current occupational field. Because the program’s participants all have work experience, they’re equipped to tailor their educational pursuits to practical applications in their given fields.

One employee completing a degree through the Edison Program is Christine Dailey Walck, a mechanical engineer turned space ergonomics expert (and STEM-podcast host). Walck already wears many hats on the lab. Now she is pursuing yet another with her doctorate studies in mechanical engineering with a focus on biomedical engineering.

“My supervisor at the time told me about the Edison Program,” Walck said. “My advisors support—plus the sponsored time—have been invaluable to my research.”

Walck’s current area of research involves studying the response of the knee complex—the knee joint and its surrounding muscles—to a newly designed knee joint orthosis, or knee brace. Her resulting computational models have set a new benchmark for determining the effects of a knee brace on the knee complex.

Commonly used by both military personnel returning from tour of duty and the average citizen recovering from a knee injury, the knee brace is the preferred treatment for rehabilitation and injury prevention around the knee complex. However, most measures of knee brace success are based on qualitative observations rather than quantitative measurement.

“When you’re studying how a knee joint orthosis works, you often get measurements from asking a patient how they feel with the brace,” Walck said. “But that information can be subjective. Therefore, we combined motion-captured data with a musculoskeletal model to find internal muscle forces, which gave more insight into how the brace actually affected the patient.”

Walck’s study does what a qualitative study could not: it tests the brace’s capabilities through an inverse dynamic solution that provides quantitative data. This information could prove crucial not only for the companies that design knee braces, but also for the doctors who provide them to patients. The study aims to give doctors the data necessary to determine which knee brace will work best for each patient.

Walck’s models rely on two main computations to determine success of a knee brace: joint range of motion and muscle force during a squat exercise. During her studies, the subject would perform the squat with a brace and without a brace, thereby allowing for comparative results showing improvement or change while wearing the brace.

Inverse kinetics were computed through results from experimental motion capture data, indicated by the sensor placed along the subject’s leg and modeled through software on the right. Inverse dynamics were measured through the blue force plate the subject is standing on.  Photo provided by Christine Dailey Walck.

Inverse kinetics were computed through results from experimental motion capture data, indicated by the sensor placed along the subject’s leg and modeled through software on the right. Inverse dynamics were measured through the blue force plate the subject is standing on. Photo provided by Christine Dailey Walck.

Walck determined range of motion through the combination of three-dimensional muscle modeling through OpenSim software and her study of inverse kinematics through motion capture, which allowed her to gain a better understanding of how the muscles of the knee complex move during a squat exercise.

She determined muscle force by having the test subject complete the exercise while on a force plate located under the foot. She evaluated the subject’s performance with an inverse dynamics tool. This tool, used in conjunction with inverse kinematics, determines the generalized net forces and torques responsible at each given joint movement during the exercise.

According to Walck, the research has already provided valuable data, but she still has other aspects of the study she wishes to pursue, including expanding her number of test subjects and exploring variables that contribute to and are affected by the knee brace.

“Based on the results, the next study should take a step back,” she said. “This study focused on nonlinear spring technology in the knee joint orthosis. The evaluation of knee joint orthosis without nonlinear spring technology could determine if the results from study stem from the nonlinear spring or from the brace itself.”

Walck also wants to study how wearing a knee brace on one knee affects the other healthy, un-braced knee.

“This is important to understand because many athletes or military personnel returning to the field wearing knee joint orthosis experience injuries in the healthy knee,” said Walck. “This raises the question of whether or not the joint knee orthosis negatively affects the opposite knee.”

As far as this study is concerned, Walck remains intrigued by the results and optimistic about future possibilities.

“I loved seeing the captured motion played out through simulations,” she said. “And I was surprised by how the brace encouraged a more balanced synergy throughout the squat movement versus an offload effect which I was expecting.”

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