title: Clinics in diagnostic imaging (163). Transient lateral patellar dislocation with trochlear dysplasia.
abstract: A 14-year-old girl presented with left knee pain and swelling after an injury. Magnetic resonance (MR) imaging showed a transient lateral patellar dislocation with patellar osteochondral fracture, medial patellofemoral ligament tear and underlying femoral trochlear dysplasia. Open reduction and internal fixation of the osteochondral fracture, plication of the medial patellar retinaculum and lateral release were performed. As lateral patellar dislocation is often clinically unsuspected, an understanding of its characteristic imaging features is important in making the diagnosis. Knowledge of the various predisposing factors for patellar instability may also influence the choice of surgical management. We also discuss signs of acute injury and chronic instability observed on MR imaging, and the imaging features of anatomical variants that predispose an individual to lateral patellar dislocation. Treatment options and postsurgical imaging appearances are also briefly described.
authors.affiliation: Department of Diagnostic Imaging, National University Hospital, Singapore.
authors.forename: Junwei
authors.initials: J
authors.lastname: Zhang
authors.affiliation: Department of Diagnostic Radiology, Yong Loo Lin School of Medicine, National University of Singapore, Singapore.
authors.forename: Chin Hwee
authors.initials: CH
authors.lastname: Lee
mesh_terms: D000293:Adolescent; D018771:Arthralgia / Q000175:diagnosis; D005260:Female; D005593:Fracture Fixation, Internal; D050723:Fractures, Bone / Q000000981:diagnostic imaging* / Q000473:pathology; D006801:Humans; D007593:Joint Instability; D007719:Knee Joint / Q000000981:diagnostic imaging; D008023:Ligaments, Articular / Q000293:injuries; D008279:Magnetic Resonance Imaging; D010329:Patella / Q000000981:diagnostic imaging* / Q000473:pathology; D031222:Patellar Dislocation / Q000175:diagnosis*
keywords: femoral trochlear dysplasia; lateral patellar dislocation; medial patellofemoral ligament tear; patellar instability