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A groundbreaking new bionic knee, developed by researchers at MIT and described in the journal Science on July 10, could significantly improve mobility and comfort for people with above-the-knee amputations. The lead researchers, including biomechatronics expert Tony Shu and study co-author Hugh Herr, designed the system to connect directly to the user's bone and muscles. Unlike traditional prosthetic legs that attach via a socket, this prosthesis is anchored to the femur with a titanium rod and uses implanted electrodes to interface with muscle tissue.
The bionic knee works in tandem with a new surgical method in which surgeons reconnect opposing muscle pairs, such as the quadriceps and hamstrings, during amputation. This allows the muscles to "communicate" and send signals more naturally, enabling users to better control the device. This setup also offers mechanical benefits, such as greater stability and weight-bearing capacity, by directly loading the skeleton rather than relying on skin-contact sockets, which are often uncomfortable and prone to infection.
In the study, two participants who received both the bone implant and the muscle-connecting surgery were compared with others who had only one or neither of the modifications. All participants used the same powered prosthetic knee. The dual-procedure group performed better in nearly all tasks—such as climbing stairs or stepping over obstacles—and reported a stronger sense of ownership and control over their prosthesis, feeling as if the device was part of their own body.
Although the device is still in its experimental phase and not yet available to the public, the results are promising. Clinical trials for FDA approval are expected to take up to five years. According to Herr, who is also a double amputee, the innovation represents a shift in prosthetics from being external tools to becoming an integrated part of the user’s body and identity.
