Tehran University of Medical Sciences Journal of Orthopedic and Spine Trauma 2538-2330 2 2 2016 06 23 45 45 Soroush Baghdadi Joint Reconstruction Research Center, Tehran University of Medical Sciences, Tehran, IR Iran SM Javad Mortazavi Joint Reconstruction Research Center, Tehran University of Medical Sciences, Tehran, IR Iran Mohammad Hassan Kaseb Joint Reconstruction Research Center, Tehran University of Medical Sciences, Tehran, IR Iran Mohammad Ayati Joint Reconstruction Research Center, Tehran University of Medical Sciences, Tehran, IR Iran 2019 07 18 Background: Acute patellar dislocation is a common injury, with up to 40% of the cases missed due to a high rate of spontaneous reduction. Complications mainly arise due to osteochondral fractures, resulting in patellofemoral osteoarthritis and rupture of medial patellar stabilizers, leading to recurrent patellar instability. Methods: Institutional database was retrospectively reviewed to find patients with missed transient patellar dislocation. From January 2010 to January 2015, ten otherwise healthy patients with a history of indirect trauma to the knee were diagnosed with missed patellar dislocation. They all had persistent pain and effusion, despite conservative treatment. Results: Eight patients eventually underwent arthroscopic debridement of osteochondral fractures and repair of ruptured ligaments, with no case of recurrent instability. Conclusions: Detailed history taking and physical examination of all acute knee injuries, with a standard three dimensional (3D) X-ray imaging and a low threshold to obtain magnetic resonance imaging (MRI) studies, could minimize cases of missed patellar dislocation and possibly severe complications. https://jost.tums.ac.ir/index.php/jost/article/view/45 https://jost.tums.ac.ir/index.php/jost/article/download/45/45