Post–Total Knee Arthroplasty Patellar Instability due to Extensor Mechanism Malalignment: A Novel Technique for Management

Persistent patellar instability after total knee arthroplasty due to extensor mechanism malalignment poses a significant clinical challenge when prosthetic components are well-fixed and adequately aligned. Revision arthroplasty carries considerable morbidity in these patients. We describe a reproducible soft tissue reconstruction technique using a fresh-frozen Achilles tendon allograft without bone block to reconstruct the medial retinacular stabilizers and redirect the extensor force vector. The allograft is fixed at the femoral medial patellofemoral ligament attachment, passed across the anterior patella, and anchored to provide robust medial restraint without prosthetic revision. In two illustrative cases with ≥24 months of follow-up, central patellar tracking was restored, subjective instability resolved, and no recurrent dislocation or extensor lag occurred.