Gait analysis is a valuable and widespread tool for assessing the quality of human locomotion. To date, marker-based optoelectronic stereo-photogrammetry (MB) represents the gold standard for the evaluation of lower limb joint kinematics and the most accurate solution. However, MB systems require specialized operators, dedicated spaces, and long preparation and processing time. Additionally, the presence of markers attached to the subject’s body and a cumbersome set-up of many cameras may affect the spontaneity of the movement. Video-based markerless systems (ML) represent a low-cost, powerful, and promising alternative to MB systems. The use of ML techniques allows making the experimental sessions faster and easier since it does not require the application of markers on the skin of the patients.