Patellar instability is a common problem seen by physical therapists, athletic trainers and orthopedic surgeons. Although following an acute dislocation, conservative rehabilitation is usually the first line of defense; refractory cases exist that may require surgical intervention. Substantial progress has been made in the understanding of the medial patellofemoral ligament (MPFL) and its role as the primary stabilizer to lateral patellar displacement. Medial patellofemoral ligament disruption is now considered to be the essential lesion following acute patellar dislocation due to significantly high numbers of ruptures following this injury. Evidence is now mounting that demonstrates the benefits of early reconstruction with a variety of techniques. Recently rehabilitation has become more robust and progressive due to our better understanding of soft tissue reconstruction and repair techniques. The purpose of this manuscript is to describe the etiology of patellar instability, the anatomy and biomechanics and examination of patellofemoral instability, and to describe surgical intervention and rehabilitation following MPFL rupture. METHODS 5.