A new generation of robotic knee prostheses offers amputees greater freedom of movement and a more natural walking pattern. Researchers at the University of Michigan have demonstrated that a commercially available robotic knee, the Power Knee, with an improved algorithm can help optimise users' gait, reduce the risk of tripping and limit strain on healthy joints.
Until now, many prosthesis users opted for passive leg prostheses: light, simple and reliable. In recent years, with the advent of robot-assisted surgery, 3D printing technology and improved procedures, much progress has also been made in the placement of knee prostheses. However, for activities such as getting up from a chair, climbing stairs or walking longer distances, this simplicity often falls short. An actively powered knee prosthesis can make all the difference.
‘Even with just two training sessions with the robotic knee, we saw clear benefits,’ says Prof. Robert Gregg, lead researcher and author of the study published in the Journal of NeuroEngineering and Rehabilitation. ‘Our results show that robotic knees actually deliver functional gains. This is evidence that has been lacking until now and is essential for broader reimbursement by health insurers.’
Algorithm for smart control
The research team tested two different control methods. The standard software from Össur recognises movements based on fixed patterns, such as when someone wants to sit down or stand up. This makes the prosthesis safe, but less fluid: the user has to wait until the knee “recognises” the movement.
The Michigan team's new AI-driven algorithm works differently. It continuously adapts to the user's pace and posture, based on mathematical models of natural human movement. By analysing real-time measurements of thigh movement, the knee can automatically adjust, resulting in smoother and more natural movements.
According to researcher Kevin Best, co-author of the study published in the Journal of NeuroEngineering and Rehabilitation, this approach reduces the risk of hip and back strain. ‘By allowing the knee to move like a real joint, users have to compensate less. This not only improves comfort, but also overall health.’
Prostheses that think for themselves
The initial results are promising: participants were able to stand up and walk faster without additional fatigue. Their gait became more symmetrical, and they lifted their toes higher, reducing the risk of tripping. Two participants have now chosen the Power Knee as their permanent prosthesis.
In follow-up research, the scientists want to test the technology on stairs and outdoors. ‘This step brings us closer to a future in which prostheses not only support the user, but also think along with them,’ says Gregg. ‘This is an important milestone towards truly smart, human-centred mobility aids.’
