A rare mode of extensor mechanism failure in total knee arthroplasty.

We reported a rare mode of extensor mechanism failure in total knee arthroplasty. The patellar tendon was elongated and thin instead of disruption at the bone-tendon junction. We also described the surgical technique for reconstruction of patellar tendon. Patellar tendon was shortened by a precalculated amount. It was then augmented by autologous semitendinosus tendon graft and protected by tension band wire. Active full knee extension could be achieved at postoperative 10 months after the removal of wire loop.