Classification of Lateral Patellar Instability in Children and Adolescents.

There is significant heterogeneity in the literature related to the causes and treatment of patellar instability. To address the multifactorial issue of patellar instability, the first task is to classify the instability pattern. Once a classification system is developed, future studies can differentiate between treatment recommendations and outcomes for each instability pattern. Existing classification systems do not include the entire spectrum of patellar instability patterns. The aim of this article is to review the nomenclature and existing patellar instability classification systems and analyze the different patterns into a comprehensive system.