Review article: Patellar instability after total knee arthroplasty.

Patellar instability after total knee arthroplasty (TKA) is a serious complication that impairs functional outcome and may lead to revision surgery. Its aetiology can be related to the surgical technique and component positioning, extensor mechanism imbalance, and other causes. After TKA, the presence of anterior knee pain, especially during stressful activities, is indicative of patellar instability. Diagnosis can be made by radiological evaluation of the patella position, alignment, and component fixation. Main treatment options include revision of the TKA components (in case of malposition) and lateral retinacular release with or without a proximal or distal realignment (in case of soft-tissue imbalance).