{"status":"ok","message-type":"work","message-version":"1.0.0","message":{"indexed":{"date-parts":[[2026,7,30]],"date-time":"2026-07-30T11:10:44Z","timestamp":1785409844988,"version":"3.56.0"},"reference-count":41,"publisher":"MDPI AG","issue":"10","license":[{"start":{"date-parts":[[2026,5,16]],"date-time":"2026-05-16T00:00:00Z","timestamp":1778889600000},"content-version":"vor","delay-in-days":0,"URL":"https:\/\/creativecommons.org\/licenses\/by\/4.0\/"}],"funder":[{"DOI":"10.13039\/100016834","name":"Chongqing Municipal Health Commission","doi-asserted-by":"crossref","award":["2022DBXM002"],"award-info":[{"award-number":["2022DBXM002"]}],"id":[{"id":"10.13039\/100016834","id-type":"DOI","asserted-by":"crossref"}]},{"award":["2022DBXM002"],"award-info":[{"award-number":["2022DBXM002"]}],"id":[{"id":"https:\/\/ror.org\/04ce5fg13","id-type":"ROR","asserted-by":"publisher"}]},{"name":"Chongqing Municipal Science & Technology Bureau","award":["CSTB2021TIAD-KPX0054"],"award-info":[{"award-number":["CSTB2021TIAD-KPX0054"]}]},{"name":"Chongqing Medical University First-Class Discipline Construction Project","award":["472020320240008"],"award-info":[{"award-number":["472020320240008"]}]},{"name":"Chongqing Medical University First-Class Discipline Construction Project","award":["CYYY-BSYJSKYCXXM202436"],"award-info":[{"award-number":["CYYY-BSYJSKYCXXM202436"]}]},{"name":"Natural Science Foundation of Chongqing, China","award":["CSTB2025NS CQ-GPX1148"],"award-info":[{"award-number":["CSTB2025NS CQ-GPX1148"]}]},{"name":"Science and Technology Research Program of Chongqing Municipal Education Commission","award":["KJQN202300403"],"award-info":[{"award-number":["KJQN202300403"]}]},{"DOI":"10.13039\/501100001809","name":"National Natural Science Foundation of China","doi-asserted-by":"crossref","award":["81902293"],"award-info":[{"award-number":["81902293"]}],"id":[{"id":"10.13039\/501100001809","id-type":"DOI","asserted-by":"crossref"}]},{"award":["81902293"],"award-info":[{"award-number":["81902293"]}],"id":[{"id":"https:\/\/ror.org\/01h0zpd94","id-type":"ROR","asserted-by":"publisher"}]},{"name":"Postdoc Research Funding","award":["2022CQBSHTB3016"],"award-info":[{"award-number":["2022CQBSHTB3016"]}]},{"DOI":"10.13039\/501100002858","name":"China Postdoctoral Science Foundation","doi-asserted-by":"crossref","award":["2022M702604"],"award-info":[{"award-number":["2022M702604"]}],"id":[{"id":"10.13039\/501100002858","id-type":"DOI","asserted-by":"crossref"}]},{"award":["2022M702604"],"award-info":[{"award-number":["2022M702604"]}],"id":[{"id":"https:\/\/ror.org\/0426zh255","id-type":"ROR","asserted-by":"publisher"}]},{"name":"Chongqing Medical Scientific Research Project","award":["2025GDRC009"],"award-info":[{"award-number":["2025GDRC009"]}]}],"content-domain":{"domain":[],"crossmark-restriction":false},"short-container-title":["Diagnostics"],"abstract":"<jats:p>Background: Patellar motion trajectory (PMT) is a key kinematic parameter for evaluating patellofemoral joint (PFJ) stability, but traditional static imaging indices are unable to capture the dynamic six-degrees-of-freedom (6-DOF) characteristics of patellar motion throughout the entire knee flexion\u2013extension cycle. Four-dimensional computed tomography (4D-CT) facilitates in vivo dynamic imaging of the PFJ, while the systematic classification of PMT in asymptomatic populations has remained underexplored. Methods: A retrospective cross-sectional study was performed on 64 asymptomatic and functionally normal knees that underwent 4D-CT dynamic scanning from March 2021 to December 2025. Patellar 6-DOF kinematic data during 0\u00b0 to 90\u00b0 of knee flexion\u2013extension were extracted through manifold optimization, automatic segmentation, and spatial registration. Following standardization of the motion cycle, unsupervised K-means clustering was employed to classify PMT phenotypes, with nonparametric tests used to analyze intergroup kinematic differences and evaluate clustering quality. Results: Three distinct PMT types were identified based on clustering validity indices, including a silhouette score of 0.381, a Davies-Bouldin index of 0.916, and a Calinski\u2013Harabasz index of 44.06: Type 1 (7.81%, 35.11 \u00b1 6.56 mm), Type 2 (56.25%, 15.67 \u00b1 6.59 mm), and Type 3 (35.94%, 2.82 \u00b1 2.41 mm). Lateral translation (Tx) served as the dominant determinant for PMT typing (p &lt; 0.001), whereas non-lateral DOF parameters exhibited no consistent intergroup differences. Postural DOFs exhibited coupled fluctuations with Tx but had no independent stratification effect. Traditional static imaging parameters demonstrated no consistent correlation with these dynamic subtypes. Conclusions: Functionally asymptomatic knees exhibited three in vivo patellar 6-DOF motion trajectory phenotypes dominated by lateral translation amplitude. This 4D-CT-based typing framework provides a dynamic kinematic baseline for PFJ stability evaluation and lays a foundation for individualized optimization of ligament reconstruction and pathophysiological research of patellofemoral disorders.<\/jats:p>","DOI":"10.3390\/diagnostics16101517","type":"journal-article","created":{"date-parts":[[2026,5,18]],"date-time":"2026-05-18T08:56:27Z","timestamp":1779094587000},"page":"1517","update-policy":"https:\/\/doi.org\/10.3390\/mdpi_crossmark_policy","source":"Crossref","is-referenced-by-count":0,"title":["In Vivo Classification of Patellar Motion Trajectories in Individuals: A 4D-CT-Based Study with Unsupervised Clustering"],"prefix":"10.3390","volume":"16","author":[{"ORCID":"https:\/\/orcid.org\/0000-0003-3132-5265","authenticated-orcid":false,"given":"Jiaying","family":"Wei","sequence":"first","affiliation":[{"name":"Orthopaedic Research Laboratory of Chongqing Medical University, Chongqing Municipal Health Commission Key Laboratory of Musculoskeletal Regeneration and Translational Medicine, Department of Orthopedics, The First Affiliated Hospital of Chongqing Medical University, Chongqing 400016, China"}],"role":[{"vocabulary":"crossref","role":"author"}]},{"given":"Ziyi","family":"Jiang","sequence":"additional","affiliation":[{"name":"School of Automation Engineering, University of Electronic Science and Technology of China, Chengdu 611731, China"}],"role":[{"vocabulary":"crossref","role":"author"}]},{"given":"Xinhao","family":"Zhang","sequence":"additional","affiliation":[{"name":"School of Automation Engineering, University of Electronic Science and Technology of China, Chengdu 611731, China"}],"role":[{"vocabulary":"crossref","role":"author"}]},{"ORCID":"https:\/\/orcid.org\/0009-0003-5907-8021","authenticated-orcid":false,"given":"Weigen","family":"Ye","sequence":"additional","affiliation":[{"name":"School of Automation Engineering, University of Electronic Science and Technology of China, Chengdu 611731, China"}],"role":[{"vocabulary":"crossref","role":"author"}]},{"ORCID":"https:\/\/orcid.org\/0009-0000-9383-5151","authenticated-orcid":false,"given":"Bowen","family":"Guo","sequence":"additional","affiliation":[{"name":"School of Automation Engineering, University of Electronic Science and Technology of China, Chengdu 611731, China"}],"role":[{"vocabulary":"crossref","role":"author"}]},{"given":"Weilin","family":"Wu","sequence":"additional","affiliation":[{"name":"School of Automation Engineering, University of Electronic Science and Technology of China, Chengdu 611731, China"}],"role":[{"vocabulary":"crossref","role":"author"}]},{"given":"Jia","family":"Li","sequence":"additional","affiliation":[{"name":"Department of Radiology, The First Affiliated Hospital of Chongqing Medical University, Chongqing 400016, China"}],"role":[{"vocabulary":"crossref","role":"author"}]},{"given":"Mao","family":"Yuan","sequence":"additional","affiliation":[{"name":"Department of Radiology, The First Affiliated Hospital of Chongqing Medical University, Chongqing 400016, China"}],"role":[{"vocabulary":"crossref","role":"author"}]},{"given":"Dehua","family":"Wang","sequence":"additional","affiliation":[{"name":"Orthopaedic Research Laboratory of Chongqing Medical University, Chongqing Municipal Health Commission Key Laboratory of Musculoskeletal Regeneration and Translational Medicine, Department of Orthopedics, The First Affiliated Hospital of Chongqing Medical University, Chongqing 400016, China"}],"role":[{"vocabulary":"crossref","role":"author"}]},{"given":"Hong","family":"Cheng","sequence":"additional","affiliation":[{"name":"School of Automation Engineering, University of Electronic Science and Technology of China, Chengdu 611731, China"}],"role":[{"vocabulary":"crossref","role":"author"}]},{"given":"Wei","family":"Huang","sequence":"additional","affiliation":[{"name":"Orthopaedic Research Laboratory of Chongqing Medical University, Chongqing Municipal Health Commission Key Laboratory of Musculoskeletal Regeneration and Translational Medicine, Department of Orthopedics, The First Affiliated Hospital of Chongqing Medical University, Chongqing 400016, China"}],"role":[{"vocabulary":"crossref","role":"author"}]},{"given":"Chen","family":"Zhao","sequence":"additional","affiliation":[{"name":"Orthopaedic Research Laboratory of Chongqing Medical University, Chongqing Municipal Health Commission Key Laboratory of Musculoskeletal Regeneration and Translational Medicine, Department of Orthopedics, The First Affiliated Hospital of Chongqing Medical University, Chongqing 400016, China"}],"role":[{"vocabulary":"crossref","role":"author"}]},{"given":"Ke","family":"Li","sequence":"additional","affiliation":[{"name":"Orthopaedic Research Laboratory of Chongqing Medical University, Chongqing Municipal Health Commission Key Laboratory of Musculoskeletal Regeneration and Translational Medicine, Department of Orthopedics, The First Affiliated Hospital of Chongqing Medical 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Surg."}],"container-title":["Diagnostics"],"original-title":[],"language":"en","link":[{"URL":"https:\/\/www.mdpi.com\/2075-4418\/16\/10\/1517\/pdf","content-type":"unspecified","content-version":"vor","intended-application":"similarity-checking"}],"deposited":{"date-parts":[[2026,5,19]],"date-time":"2026-05-19T04:21:39Z","timestamp":1779164499000},"score":1,"resource":{"primary":{"URL":"https:\/\/www.mdpi.com\/2075-4418\/16\/10\/1517"}},"subtitle":[],"short-title":[],"issued":{"date-parts":[[2026,5,16]]},"references-count":41,"journal-issue":{"issue":"10","published-online":{"date-parts":[[2026,5]]}},"alternative-id":["diagnostics16101517"],"URL":"https:\/\/doi.org\/10.3390\/diagnostics16101517","relation":{},"ISSN":["2075-4418"],"issn-type":[{"value":"2075-4418","type":"electronic"}],"subject":[],"published":{"date-parts":[[2026,5,16]]}}}