Robotic knee prosthesis: Advanced control algorithm could expand commercial leg's benefits

Paired with custom control software, Össur's powered knee prosthesis helped study participants sit, stand and walk more easily

University of Michigan

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Photos of labor

A commercial robotic leg could potentially benefit both higher- and lower-mobility amputees, University of Michigan roboticists have shown for the first time. 

 

The leg provided the largest gains when the U-M team applied its own control strategy, enabling a more symmetrical gait, lower tripping risks and a reduction in strain on the study participants' sound legs and hips.

 

The Michigan team worked with Össur's Power Knee, provided by the company, with primary funding from the National Institutes of Health.  

 

Multiple robotic prosthetic legs are on the market but aren't yet in wide clinical use. For many activities, the lightness and simplicity of passive legs is preferred by prosthesis users. However, for particularly taxing activities like rising from a chair, climbing stairs and hills, and walking long distances, the addition of power has the potential to help prosthesis users be more active while also preventing overuse injuries. 

 

"The passive leg has a huge advantage in this study because the participants use it every day and are very used to its behaviors. Our study participants had just two training sessions with the powered leg. Even with that disadvantage, we observed benefits of the powered leg with both our controller and Össur's," said Robert Gregg, a professor of robotics and corresponding author of the study in the Journal of NeuroEngineering and Rehabilitation.

 

"Our study is significant because evidence was previously lacking for benefits of robotic knees over advanced passive knees, which is a big reason insurance companies don't typically cover robotic knees. Our results begin to provide this evidence."

 

In this initial study, the researchers focused on key activities of daily living in which a powered prosthesis could provide meaningful benefits compared to passive knee prostheses. Study participants repeatedly sat and stood; walked quickly on a treadmill; and repeatedly sat in a chair, walked and sat down again. 

 

Prosthesis users who required extra walking assistance, such as a cane, found that the Power Knee offered significant help in all these tasks. Those who get around more easily on their own prostheses saw the most improvement in their gaits when Gregg's team implemented their own control algorithm on Össur's leg. One recent amputee described it as the closest they’d felt to two-legged walking on a prosthesis.

 

"Our goal in prosthesis control is to make the leg behave as close as possible to the missing human limb in order to prevent compensations that often lead to overuse injuries. It also matters because gait deviations can bring unwanted attention to some users," said Kevin Best, a research associate in robotics, recent U-M robotics PhD graduate and first author of the study.

 

The team investigated two fundamentally different control approaches. Össur's more conventional controller relies on recognizing specific features of the user's motion, indicating what they're about to do. This makes the system very safe and predictable but may not always keep up with the user's intent, Gregg said. In order to sit, users have to wait for the knee to recognize the sitting motion before it will bend, and likewise with standing.

 

In contrast, the control approach developed by Gregg's team continually adjusts to the user's motion. They built mathematical models of how humans move, based on large datasets of unimpaired individuals. At each moment in time, their control algorithm measures the user's thigh motion to determine the right behavior, creating more natural knee motions that are better synchronized with the user. 

 

"With the improvements in robotic devices, it is clear that robotic prostheses offer great promise to the amputee population," said Jeff Wensman, a certified prosthetist/orthotist at Michigan Medicine and study co-author. "I am excited to see the advancement of a strategy to provide powered prosthesis users with user-synchronized control. I believe that this is a missing link to making powered prosthetics a reality for amputees."

 

This new control algorithm is harder to learn after using a conventional prosthesis for years, but the repeated sit-to-stand trials showed that participants were learning. Rather than getting more tired with each trial, they got faster. Then while walking, the more mobile group showed two improvements that could become significant benefits.

 

First, they lifted the toe of the prosthetic foot higher, reducing the risk of tripping over small obstacles or rougher terrain. Second, they didn't need to swing their hips as hard to move the prosthetic leg forward, hinting that the powered knee and lifelike control algorithm could potentially reduce back pain and allow users to go farther before getting tired, though the team couldn't measure this with the short study. 

 

Next, the team hopes to demonstrate the safety and effectiveness of their control algorithm with stairs and ramps, followed by take-home tests. With more time to practice, the participants may be able to achieve even more. If the control strategy is successful, Össur could incorporate aspects of it into its own algorithm.

 

For now, the improvements with Össur's own algorithm were enough for two of the study participants to switch to the Power Knee for their everyday prosthesis, demonstrating that robotic prostheses are moving from laboratory exploration to real-world benefit.

 

Primary funding by the National Institutes of Health was under award No. R01HD094772, with additional support from the National Science Foundation. Össur provided initial financial support and may have a financial interest in the results.

 

The team has applied for patent protection for their controller with the assistance of U-M Innovation Partnerships.

 

Study: The clinical effects of the Össur Power Knee with phase-based and default control during sitting, standing, and walking (DOI: 10.1186/s12984-025-01729-2)

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Journal

Journal of NeuroEngineering and Rehabilitation

TWO

10.1186/s12984-025-01729-2 

Kids are not getting as much sleep as their parents think, study finds

Researchers at Brown University found that many Rhode Island kids sleep less than their parents realize, with Latino children logging the least amount of rest

Brown University

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PROVIDENCE, R.I. [Brown University] — While many parents assume that putting a child to bed means they will quickly be asleep, a new study from researchers at Brown University found that’s often not the case. 

The study, published in Frontiers in Pediatrics, tracked the sleep patterns of 102 elementary school children, over the course of a week. While 83% of parents believed their child was sleeping the right amount, sleep trackers showed that only 14% of the children met national sleep guidelines. The findings add to growing concerns that American children aren’t getting the sleep they need.

“What parents often don’t see is how long it takes for kids to fall asleep or how often they wake up during the night,” said Diana S. Grigsby-Toussaint, the study’s senior author and an associate professor at the Brown University School of Public Health. 

To better understand what happens after the lights turn off, the researchers used wrist-worn accelerometers to track children’s bedtimes, how long it took them to fall asleep, how often they woke up and how much time they spent sleeping. Parents filled out surveys and daily sleep diaries. The goal was to see how well parents’ perceptions matched up with their children’s realities, Grigsby-Toussaint said.

According to the American Academy of Pediatrics, children between ages 6 and 12 should get between nine and 12 hours of sleep per night. Data from the accelerometers showed that on average, the children were getting only eight hours and 20 minutes of actual sleep. Parents, however, reported their kids slept more than nine and a half hours.

Digging into data, the researchers found that the gap was due to time parents didn’t account for. Children were awake for an average of more than 38 minutes per night, while parents reported under five minutes of nighttime wakefulness for their children.

To better understand racial and ethnic disparities in sleep, which Grigsby-Touissant said are rarely factored into sleep studies, the researchers looked at differences between Latino and non-Latino children — 56% of enrolled study participants were Latino. They found that Latino children averaged just over eight hours of sleep per night while non-Latino children averaged eight and a half. Only 4.4% of Latino children in the study met national sleep guidelines compared to 22.8% of non-Latino children.

The study also explored whether parents were aware of problems related to sleep. Latino caregivers, for instance, were more likely than other groups to report that sleep was a concern, and to say their child had trouble staying asleep. Meanwhile, non-Latino parents tended to underreport sleep problems.

Parents in both groups tended to overestimate how much sleep their kids were getting.

The team said that some of the findings could be explained by cultural factors, such as later bedtimes, co-sleeping and room sharing, which are more common in Latino households. These factors might influence both sleep behavior and parental perceptions. They hope future research can explore how home environments and parenting styles affect children’s sleep patterns.

“Our work indicates that we need to improve our communication about sleep with families to capture the multiple dimensions of it,” Grigsby-Toussaint said.

The research team, which included scientists from Brown’s Warren Alpert Medical School and Brown University Health’s Rhode Island Hospital, also noted the limitations of wrist devices, which don’t always distinguish between periods of wakeful rest and sleep. This means that the tracking devices, too, could over-estimate children’s sleep volume.

To improve children’s sleep, the researchers encouraged families to take proactive steps, Grigsby-Toussaint said:

"This comes down to following those tried-and-true sleep tips to support healthy sleep habits and doing all the things we know helps people get their best rest: bedtime routines, maintaining consistent sleep and wake schedules — even on the weekends — encouraging physical activity and exposure to natural light and green spaces during the day, limiting screens close to bedtime, and creating a comfortable sleep environment.”

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Journal

Frontiers

TWO

10.3389/fped.2025.1622943 

Article Title

Associations between objectively and subjectively measured sleep outcomes among elementary school children in Rhode Island

  

Inhaler-related greenhouse gas emissions in the US

JAMA Network

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About The Study: Inhaler-related emissions in the U.S. have increased over the past decade. Policymakers and regulators seeking to reduce emissions should identify targeted solutions aimed at shifting utilization to currently marketed dry powder and soft mist inhalers while facilitating the entry of newer, affordable metered-dose products containing propellants with low global warming potential.

Corresponding Author: To contact the corresponding author, William B. Feldman, MD, DPhil, MPH, email wfeldman@mednet.ucla.edu.

To access the embargoed study: Visit our For The Media website at this link https://media.jamanetwork.com/

(doi:10.1001/jama.2025.16524)

Editor’s Note: Please see the article for additional information, including other authors, author contributions and affiliations, conflict of interest and financial disclosures, and funding and support.

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Embed this link to provide your readers free access to the full-text article 

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Journal

JAMA

UCLA Health study finds inhalers for asthma and COPD drive significant greenhouse gas emissions

Research shows inhalers contribute carbon emissions equivalent to 530,000 cars annually

University of California - Los Angeles Health Sciences

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Inhalers are the frontline treatment for asthma and COPD, but they come with a steep environmental cost, according to a new UCLA Health study — the largest to date quantifying inhaler-related emissions in the United States.

Researchers found that inhalers have generated over 2 million metric tons of carbon emissions annually over the past decade, equivalent to the emissions of roughly 530,000 gas-powered cars on the road each year.

The study, published in JAMA, analyzed emissions from the three types of inhalers approved for asthma or COPD from 2014 to 2024. It found that metered-dose inhalers were the most harmful to the environment, accounting for 98 percent of emissions over the ten-year period. Metered-dose inhalers contain hydrofluoroalkane (HFA) propellants, which are potent greenhouse gases that were widely used in products such as aerosol sprays. The other types of inhalers, which include dry inhalers and soft powder mist inhalers, are less harmful to the environment as they deliver medication to the lungs without the need for propellants.

“Inhalers add to the growing carbon footprint of the US healthcare system, putting many patients with chronic respiratory disease at risk,” said Dr. William Feldman, a pulmonologist and health services researcher at the David Geffen School of Medicine at UCLA, and the study’s lead author. “On the upside, there is tremendous opportunity to make changes that protect both patients and the planet by utilizing lower-emission alternatives.”

Researchers conducted the study using a comprehensive U.S. database capturing inhaler prescriptions at the National Drug Code (NDC) level. Emissions were then estimated using validated academic studies and analyzed by drug type, device type, propellant type, therapeutic class, branded status, manufacturer, payer, and pharmacy benefit manager.

Researchers plan to expand their research to examine inhaler-related emissions in specific patient populations, such as the Medicaid population. They will also compare clinical outcomes between of lower- and higher-emission inhalers in the same therapeutic class and explore pricing and patenting strategies that pharmaceutical companies may use as they roll out lower-emission inhaler technologies. 

“A key first step to driving change is understanding the true scale of the problem,” Feldman said. “From there, we can identify what’s fueling these emissions and develop targeted strategies to reduce them—benefiting both patients and the environment.”

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Journal

JAMA

TWO

10.1001/jama.2025.16524 

Method of Research

Data/statistical analysis

Subject of Research

Not applicable

Article Title

UCLA Health Study Finds Inhalers for Asthma and COPD Drive Significant Greenhouse Gas Emissions

 

Nurse workload and missed nursing care in neonatal intensive care units

JAMA Pediatrics

About The Study:

 In this cross-sectional study, nurses’ subjective workload and shift-level staffing ratios exerted direct effects on reliable care delivery. High subjective workload and staffing ratios greater than 2 infants per nurse should be targets for workload reduction in neonatal intensive care units. 

Corresponding Author: To contact the corresponding author, Heather L. Tubbs-Cooley, Ph.D., email tubbscooley.1@osu.edu.

To access the embargoed study: Visit our For The Media website at this link https://media.jamanetwork.com/

(doi: 10.1001/jamapediatrics.2025.3647)

Editor’s Note: Please see the article for additional information, including other authors, author contributions and affiliations, conflict of interest and financial disclosures, and funding and support.

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Journal

JAMA Pediatrics