“…Our system addresses some of the drawbacks of related range sensor and home-video based systems [2,9,11,[13][14][15][16][17][18][19]41] and IMU systems [22][23][24][25][26] namely: (i) unlike [9], there are no colour restrictions on the background or the participant's clothing; (ii) in contrast to [9], which is validated on only one healthy volunteer with one walking trial with no gold standard benchmark, we validate our proposed system's knee angle against the gold standard VICON MX Giganet 6xT40 and 6xT160 (VICON Motion Systems Ltd., Oxford, UK, approximately £ 250,000) optical motion analysis system (the same gold standard as used by Ugbolue et al [11]); (iii) unlike systems of [11] and Pro-Trainer and Siliconcoach (Siliconcoach Ltd., Dunedin, New Zealand) as used by the authors in [42,43] that require significant manual effort, our system autonomously tracks the markers attached to the joints and calculates the knee angle; the only operational effort required is for marker-template selection for tracking initialisation which is done via a user-friendly graphical user interface (GUI); (iv) unlike the passive marker system [41] that is only validated on one side of the body without any benchmarking systems, our system is validated on both sides of the body with a gold standard VICON optical motion analysis system; (v) 3D Kinect range sensor-based systems [13-18, 20, 21] cannot reliably capture relatively fast body motion, since Kinect operates at only 30 frames per second (fps), whereas our system operates at 210 fps; (vi) like other range sensor and home-video based systems, our system is non-intrusive to the participants, which is in contrast to state-of-the-art IMU gait analysis systems [22][23][24][25][26]. However, with only a 2D camera in our gait analysis system, its drawback lies in the following two aspects: (i) estimation of the human joint locations using our system is less accurate compared to 3D Kinect-based range sensor systems, and (ii)...…”