To make motion analysis more accessible and scalable, we develop advanced markerless motion capture systems that estimate human movement without physical markers, reducing the reliance on expensive, constrained laboratory setups. Utilizing computer vision and deep learning-based pose estimation, we extract precise 2D and 3D joint coordinates. To guarantee clinical reliability, our methods are rigorously validated against gold-standard 14-camera optical motion capture systems, ensuring systematic accuracy and consistency. Through validated, non-contact technology, HDL bridges the gap between laboratory-grade precision and real-world usability for clinical and rehabilitation applications.