Patellofemoral Instability: Preoperative Considerations and Postoperative Imaging.

Patellofemoral instability is common, often affecting young female patients. It contributes to significant morbidity, such as pain and premature osteoarthritis. Patient presentation varies, from acute instability events to chronic/recurrent instability. This article provides a detailed description of the anatomy and biomechanics of the patellofemoral joint and relates it to the pathology of patellofemoral instability. There are well-recognized predisposing anatomical factors, such as trochlear morphology, patella height, excessive lateralization of the tibial tubercle, excessive valgus alignment, and femoral or tibial torsion.Diagnosis of patellofemoral instability requires a thorough clinical history and physical examination, combined with a multimodality imaging approach. Imaging is useful in surgical planning to define the severity of predisposing anatomical factors and to detect postoperative complications. The operative management of patellofemoral instability targets predisposing anatomical factors, such as medial stabilizing ligament reconstruction or repair, tibial tubercle osteotomy, femoral trochleoplasty, coronal plane realignment osteotomy, and torsional osteotomy.