{"status":"ok","message-type":"work","message-version":"1.0.0","message":{"indexed":{"date-parts":[[2026,7,20]],"date-time":"2026-07-20T09:01:20Z","timestamp":1784538080825,"version":"3.55.0"},"reference-count":34,"publisher":"MDPI AG","issue":"14","license":[{"start":{"date-parts":[[2026,7,19]],"date-time":"2026-07-19T00:00:00Z","timestamp":1784419200000},"content-version":"vor","delay-in-days":0,"URL":"https:\/\/creativecommons.org\/licenses\/by\/4.0\/"}],"funder":[{"DOI":"10.13039\/501100004826","name":"Beijing Natural Science Foundation-Haidian Original Innovation Joint Fund","doi-asserted-by":"publisher","award":["L232063"],"award-info":[{"award-number":["L232063"]}],"id":[{"id":"10.13039\/501100004826","id-type":"DOI","asserted-by":"publisher"}]}],"content-domain":{"domain":[],"crossmark-restriction":false},"short-container-title":["Sensors"],"abstract":"<jats:p>(1) Background: This study validated the accuracy of a markerless gait analysis system, Foot4D, against the Vicon 3D motion capture system in 60 patients with ankle injuries. (2) Methods: Synchronized gait data were collected using both systems while participants walked on a treadmill at self-selected speeds. The Foot4D system employs a Vision Transformer (ViT-H\/16) encoder and the SKEL parametric model for markerless 3D pose reconstruction from multi-view depth cameras. Spatiotemporal gait parameters and lower limb 3D kinematics (hip, knee, and ankle) were compared using ICC, Bland\u2013Altman analysis, and MAE. (3) Results: All 12 spatiotemporal parameters showed good-to-excellent agreement (ICC = 0.738\u20130.999, MAE = 0.009\u20130.108 m\/s). Agreement for joint kinematics decreased from proximal to distal: hip (mean ICC \u2248 0.947, MAE 1.16\u20131.52\u00b0), knee (mean ICC \u2248 0.921, MAE 1.17\u20131.75\u00b0), and ankle (mean ICC \u2248 0.839). Ankle sagittal plane ROM demonstrated good agreement (ICC = 0.857\u20130.911), while the frontal (ICC \u2248 0.807) and transverse (ICC \u2248 0.816\u20130.835) planes were at the lower bound of good agreement, with a \u22123.19\u00b0 systematic bias in the injured ankle sagittal plane. (4) Conclusions: Foot4D is clinically reliable for spatiotemporal and proximal joint kinematic assessment, though ankle multiplanar motion measurement warrants further algorithmic optimization.<\/jats:p>","DOI":"10.3390\/s26144579","type":"journal-article","created":{"date-parts":[[2026,7,20]],"date-time":"2026-07-20T07:54:13Z","timestamp":1784534053000},"page":"4579","update-policy":"https:\/\/doi.org\/10.3390\/mdpi_crossmark_policy","source":"Crossref","is-referenced-by-count":0,"title":["Validation of a Markerless Non-Contact Gait Analysis System for Three-Dimensional Gait Kinematics in Patients with Ankle Injuries: A Concurrent Comparison Study with the Vicon Three-Dimensional Motion Capture System"],"prefix":"10.3390","volume":"26","author":[{"ORCID":"https:\/\/orcid.org\/0000-0002-2427-1193","authenticated-orcid":false,"given":"Xuhan","family":"Cao","sequence":"first","affiliation":[{"name":"Department of Sports Medicine, Peking University Third Hospital, Institute of Sports Medicine of Peking University, Beijing 100191, China"},{"name":"Beijing Key Laboratory of Research and Translation for Drugs and Medical Devices in Precision Diagnosis and Treatment of Sports Injuries, Beijing 100191, China"},{"name":"Engineering Research Center of Sports Trauma Treatment Technology and Devices, Ministry of Education, Beijing 100191, China"}],"role":[{"vocabulary":"crossref","role":"author"}]},{"given":"Qing","family":"Zhou","sequence":"additional","affiliation":[{"name":"Department of Sports Medicine, Peking University Third Hospital, Institute of Sports Medicine of Peking University, Beijing 100191, China"},{"name":"Beijing Key Laboratory of Research and Translation for Drugs and Medical Devices in Precision Diagnosis and Treatment of Sports Injuries, Beijing 100191, China"},{"name":"Engineering Research Center of Sports Trauma Treatment Technology and Devices, Ministry of Education, Beijing 100191, China"}],"role":[{"vocabulary":"crossref","role":"author"}]},{"given":"Shuo","family":"Wang","sequence":"additional","affiliation":[{"name":"Department of Engineering Physics, Key Laboratory of Particle and Radiation Imaging, Ministry of Education, Tsinghua University, Beijing 100084, China"}],"role":[{"vocabulary":"crossref","role":"author"}]},{"ORCID":"https:\/\/orcid.org\/0000-0002-5303-3899","authenticated-orcid":false,"given":"Mingjie","family":"Dong","sequence":"additional","affiliation":[{"name":"College of Mechanical & Energy Engineering, Beijing University of Technology, Beijing 100124, China"}],"role":[{"vocabulary":"crossref","role":"author"}]},{"ORCID":"https:\/\/orcid.org\/0000-0001-9644-6434","authenticated-orcid":false,"given":"Shuang","family":"Ren","sequence":"additional","affiliation":[{"name":"Department of Sports Medicine, Peking University Third Hospital, Institute of Sports Medicine of Peking University, Beijing 100191, China"},{"name":"Beijing Key Laboratory of Research and Translation for Drugs and Medical Devices in Precision Diagnosis and Treatment of Sports Injuries, Beijing 100191, China"},{"name":"Engineering Research Center of Sports Trauma Treatment Technology and Devices, Ministry of Education, Beijing 100191, China"}],"role":[{"vocabulary":"crossref","role":"author"}]},{"ORCID":"https:\/\/orcid.org\/0000-0003-3600-9544","authenticated-orcid":false,"given":"Qinwei","family":"Guo","sequence":"additional","affiliation":[{"name":"Department of Sports Medicine, Peking University Third Hospital, Institute of Sports Medicine of Peking University, Beijing 100191, China"},{"name":"Beijing Key Laboratory of Research and Translation for Drugs and Medical Devices in Precision Diagnosis and Treatment of Sports Injuries, Beijing 100191, China"},{"name":"Engineering Research Center of Sports Trauma Treatment Technology and Devices, Ministry of Education, Beijing 100191, China"}],"role":[{"vocabulary":"crossref","role":"author"}]}],"member":"1968","published-online":{"date-parts":[[2026,7,19]]},"reference":[{"key":"ref_1","doi-asserted-by":"crossref","first-page":"57","DOI":"10.1016\/j.forsciint.2019.01.007","article-title":"Forensic gait analysis\u2014Morphometric assessment from surveillance footage","volume":"296","author":"Seckiner","year":"2019","journal-title":"Forensic Sci. 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