Transient lateral patellar dislocation is a commonly encountered injury. It presents a challenge to the radiologist due to the difficulty with making the correct diagnosis on radiography. The MR findings of acute transient lateral patellar dislocation have been well described1–3 and include rupture of the medial patellofemoral ligament, large knee effusion, “kissing bone contusions” in the medial facet of the patella and lateral aspect of the lateral femoral condyle, lateral patellar tilt or subluxation, osteochondral fracture of the patella and/or the lateral femoral condyle, and intra-articular bony fragment. There is only one report in the literature on the radiographic diagnosis of transient lateral patellar dislocation.4 Diagnosing transient lateral patellar dislocation on radiography is challenging because its imaging features on radiography are subtle. Looking for these small findings is similar to looking at the tip of an iceberg: The small visible tip at the surface harbors serious danger down below! This CME article reviews the salient aspects of transient lateral patellar dislocation relevant to daily radiology practice.
Dr. Chen is Academic Head of Musculoskeletal Section, Department of Radiology, Brooke Army Medical Center, Fort Sam Houston, Texas, and Assistant Professor, Department of Radiology, Uniformed Services University of the Health Sciences, Bethesda, Maryland. Dr. Bui-Mansfield is Chief of Musculoskeletal Radiology Section, Department of Radiology, Brooke Army Medical Center, 3851 Roger Brooke Drive, Fort Sam Houston, TX 78234-6200, and Associate Professor, Department of Radiology, Uniformed Services University of the Health Sciences, Bethesda, Maryland; E-mail: firstname.lastname@example.org; Dr. Chabak is Staff Radiologist, Department of Radiology, General Leonard Wood Army Community Hospital, Fort Leonard Wood, Missouri; and Dr. O'Brien is Associate Program Director of Emergency Radiology, Department of Radiology, Brooke Army Medical Center, Fort Sam Houston, Texas, and Assistant Professor, Department of Radiology, Uniformed Services University of the Health Sciences, Bethesda, Maryland.
This issue of CDR will qualify for 2 ABR Self-Assessment Module SAM (SA-CME) credits. See page 6 for more information.
This module meets the American Board of Radiology's (ABR's) criteria for self-assessment toward the purpose of fulfilling requirements in the ABR Maintenance of Certification (MOC) program.
Please note that in addition to the SA-CME credits, subscribers completing the activity will receive the usual ACCME credits.
After participating in this activity, the diagnostic radiologist should be better able to distinguish the subtle radiographic findings of transient lateral patellar dislocation.
The opinions and assertions contained herein are those of the authors and should not be construed as official or as representing the opinions of the Department of the Army, Department of the Air Force, or the Department of Defense.
The authors and all staff in a position to control the content of this CME activity and their spouses/life partners (if any) have disclosed that they have no relationships with, or financial interests in, any commercial organizations pertaining to this educational activity.
Lippincott Continuing Medical Education Institute, Inc., is accredited by the Accreditation Council for Continuing Medical Education to provide continuing medical education for physicians. Lippincott Continuing Medical Education Institute, Inc., designates this enduring material for a maximum of 2 AMA PRA Category 1 Credits™. Physicians should only claim credit commensurate with the extent of their participation in the activity. To earn CME credit, you must read the CME article and complete the quiz and evaluation on the enclosed answer form, answering at least seven of the 10 quiz questions correctly. This continuing medical education activity expires on November 7, 2014.