E1355. Patellar Instability: Review of Risk Factors and Patterns of Injury
  1. Oluwafunmiso Fagbongbe; University of South Alabama College of Medicine
  2. Alireza Eajazi; UT Health San Antonio
  3. Michael Davis; UT Health San Antonio
  4. Fadi Nemeh; UT Health San Antonio
  5. Iman Khodarahmi; NYU Langone Medical Center
  6. Shereef Elhalwagi; UT Health San Antonio
The purpose of this educational exhibit is to present a multi-modality review of patellofemoral anatomy and to discuss principles of patellofemoral instability as well as patellar trauma and some anatomic variants.

Educational Goals / Teaching Points
- Review the normal patellofemoral anatomy as well as some normal variants such as bipartite/multipartite patella and dorsal defect of the patella. - Discuss classification of patellar fractures. - Discuss principles of patellar instability: mechanisms of injury, patellar fracture-dislocation, lateral tracking of the patella, and patellofemoral malalignment. - Review risk factors for patellar instability including trochlear dysplasia, lateralization of the the tibial tuberosity, and patella alta/baja. - Review injuries associated with patellar dislocation including medial patellar retinaculum tears, joint effusions/hemarthrosis, osteochondral loose bodies and chondral injuries.

Key Anatomic/Physiologic Issues and Imaging Findings/Techniques
- Trochlear dysplasia - Patella alta - Patella baja - Medial patellofemoral ligament injury - Medial retinacular complex injury - Kissing contusions - Patellar fracture - Bipartite patella - Multipartite patella - Dorsal defect of the patella

Patellofemoral instability is common; particularly among physically active individuals and multiple imaging modalities are often essential for analyzing the anatomy and sequela of instability including dislocation in order to guide management. The patella is particularly susceptible to traumatic injury. Identification and appropriate description of injury is crucial for prompt and appropriate therapeutic management. Certain anatomic variants can present a diagnostic dilemma and are discussed here.