Medial Patellar Instability: Primary and Iatrogenic

Abstract Medial patellar instability, in both noniatrogenic and iatrogenic settings, is rare compared with lateral patellar instability. Although iatrogenic medial patellar dislocation is most often considered a complication of a lateral retinacular release, improperly performed patellofemoral procedures such as tibial tubercle osteotomy and medial patellofemoral ligament reconstruction can also be contributing factors. As a result, a thorough history and physical examination are paramount. Because of the sparse evidence for medial patellar instability treatment, management should follow that of lateral patellar instability: first-time dislocators without significant risk of recurrence or osteochondral fracture should initially be managed nonoperatively, whereas recurrent dislocators and those having failed conservative treatment are surgical candidates. Treatment is empiric at this point and is directed at contributing pathological conditions; most commonly, that is reversal of iatrogenic pathological conditions such as repair or reconstruction of a prior excessive lateral release. In this chapter we highlight what is understood about the unusual pathological condition of medial patellar instability, both in the noniatrogenic and iatrogenic settings.