Patellar Instability Following Total Knee Arthroplasty: A Review of Etiology, Diagnosis, and Management Strategies.

Patellar instability remains one of the most challenging and persistent complications following total knee arthroplasty (TKA), significantly affecting patient satisfaction and functional outcomes. Despite advances in implant technology and surgical techniques, patellofemoral maltracking remains a leading cause of anterior knee pain and one of the most frequent non-infectious reasons for revision surgery. The etiology is complex and often involves a combination of component malposition, soft-tissue imbalance, patient-specific anatomical risk factors, and suboptimal implant design. Internal rotation of the femoral or tibial components is consistently associated with increased lateral patellar tilt and subluxation, while soft-tissue contributors such as lateral retinacular tightness or medial instability can exacerbate the condition. Diagnostic evaluation relies on a thorough clinical examination supported by imaging modalities such as CT, which is the gold standard for assessing component rotation. Intraoperative computer-assisted navigation offers real-time feedback and is increasingly being used to reduce malalignment-related complications. Management strategies vary according to the underlying cause, ranging from conservative physiotherapy in mild cases to component revision, soft-tissue realignment, and distal realignment osteotomies in more severe or complex scenarios. Outcomes are most favorable when surgical intervention is tailored to the specific etiology of instability. Preventative strategies, including precise rotational alignment, appropriate implant selection, and intraoperative tracking assessment, are crucial for optimizing patellar tracking and improving long-term TKA outcomes. This narrative review provides an integrated analysis of the biomechanical, diagnostic, and therapeutic considerations essential to managing patellar instability in contemporary TKA practice.