Imaging Analysis of Patella Instability Factors

Imaging has been considered of primary importance in the analysis of patellofemoral (PF) joint instability factors since the earlier experiences in this subject [1–4]. In the past few years, magnetic resonance imaging (MRI) has progressively become one of the most important exams for analysis of pathologic anatomy of an unstable PF joint and for eventual surgical planning. Following the Lyon’s School, it is possible to identify three major anatomic factors of instability: trochlear dysplasia, excessive patellar height, and pathological tibial tubercle-trochlear groove (TT-TG) distance [1]. MRI is applicable for assessment of each of these factors with increasing evidence on reliability and reproducibility. The MRI study of the patellofemoral joint should present specific characteristics such as the inclusion of the proximal part of the trochlea and the anterior tibial tuberosity, in order to allow the measurement of the specific indexes required for the assessment of patellar instability. These characteristics should be put on the specialist prescription in order to avoid missing reference points. The aim of this chapter is to give the reader an overview on this continuously evolving field of research and provide a guide for everyday clinical practice in treatment of PF joint instability.