Design and Evaluation of a Bionic Knee with Myoneural Control

Abstract

Building bionic limbs requires the convergence of surgical innovation and robotic engineering: surgical constructs must reliably extract and amplify intent signals from the body, while robotic systems must accurately interpret these signals to deliver precise, responsive assistance and meaningful feedback. Individuals with above-knee amputation often experience reduced mobility and diminished agency when using conventional prosthetic devices. These limitations can impede human-prosthesis embodiment, the integration of the prosthesis into the user’s body schema. This thesis advances the goal of seamless human-machine integration by presenting the design and evaluation of a powered knee prosthesis. The hardware, software, and embedded systems of a prior prototype were upgraded to create a modular, field-deployable research platform. The resulting system incorporates a control framework that enables volitional actuation of the knee joint via electromyographic signals recorded from surgically reconstructed agonist-antagonist muscle pairs. To evaluate the system, one participant with an above-knee amputation completed a series of experimental tasks using both their prescribed microprocessor-controlled prosthesis and the bionic knee. Neural control performance was assessed through blindfolded free-space tasks, while functional capability was evaluated during sit-to-stand transitions, squatting, level-ground walking, and stair ascent. The bionic prosthesis, weighing 2.6 kg, comparable to commercially available powered knees, demonstrated robust, real-time control across all tasks. Volitional neural inputs enabled intuitive and responsive joint actuation, resulting in superior performance and perceived embodiment relative to the passive device. During sit-to-stand and squatting tasks, ground reaction force data revealed increased weight-bearing on the prosthetic side, reflecting enhanced user confidence. Gait analysis showed improved temporal symmetry during walking with the bionic knee, indicating more balanced interlimb coordination. Embodiment scores were consistently higher across all measured domains, with the participant describing the prosthesis as “feeling like my leg” and “helping me.” These findings underscore the potential of neurally integrated prosthetic systems to restore volitional control, improve functional performance, and promote a more embodied user experience.