Design of a Knee-joint Exoskeleton to Reduce Misalignment in Both the Sagittal and Coronal Planes

Many individuals experience knee dysfunctions attributed to the natural aging process and degenerative conditions. To aid individuals in regaining knee functionality, supportive exoskeletons were designed to be affixed to both the shin and thigh. However, a common issue encountered in knee exoskeletons involves the misalignment of joints between the exoskeleton and the user, resulting in discomfort and potential injuries. To reduce misalignment with the knee joint, it is essential for the thigh and shin harnesses of the exoskeleton to replicate the natural trajectories of the knee. However, achieving this is a complex task due to the shifting center of rotation of the knee in both the Sagittal and Coronal planes. Previous knee exoskeletons primarily focus on aligning the joint in the Sagittal plane, neglecting alignment in the other dimension due to inherent design constraints. For the first time, this study introduces a knee-joint exoskeleton capable of conforming to the natural movement of the knee in both the Sagittal and Coronal planes, with the aim of minimizing joint misalignment without the use of inherently soft materials. A spherical scissor linkage mechanism (SSLM) was utilized in conjunction with a customized guide rail to adjust the center of rotation of the SSLM. This configuration facilitates knee flexion/extension while accommodating the knee joint’s center of rotation in both the Sagittal and Coronal planes. The experimental outcomes demonstrated a substantial reduction in misalignment with the knee when compared to a commercial knee-support brace with a one-degree-of-freedom revolute joint.