Development and Cadaveric Implementation of a New Endoskeletal-type Artificial Knee Joint With Precise Knee Motion Analysis

As the aging population increases, maintaining mobility in individuals with musculoskeletal impairments becomes increasingly important. To overcome the limitations of exoskeletal systems, we developed an implantable, active artificial joint—an endoskeleton—to restore complex knee motion. We conducted detailed motion analysis on human cadaveric knees and porcine stifles using optical tracking and CT-based 3D models. Based on the findings, a four-bar linkage and medial-pivot cam mechanism was implemented to replicate natural joint kinematics. Titanium 3D-printed patient-specific instruments guided surgical procedures in porcine models, adapted from total knee arthroplasty protocols. Postoperative evaluations demonstrated that the prototype achieved 101° flexion-extension and 28° axial rotation. Human knees exhibited a J-curve trajectory and medial pivot motion, while porcine stifles showed greater rotational displacement. The results support our joint design’s capacity to mimic physiological movements. This study highlights the importance of accurately reproducing multi-axis knee motion and presents a promising platform for future active prosthetic development.