Abstract
We report a novel case of the simultaneous post and cone fractures of a polyethylene (PE) insert in a mobile-bearing posterior-stabilized total knee arthroplasty. Twelve years after the primary total knee arthroplasty, the 72-year-old male patient presented with a recurring right knee instability and was diagnosed with the wear of the PE insert based on physical and radiological examinations. Revision surgery was performed. The post and cone of the PE insert had fractured simultaneously. Moreover, the femoral and tibial components were in direct contact with each other. One year post-revision, knee function had improved. To diagnose a PE breakage, such as a post or cone fracture, surgeons should consider the possibility of PE breakage even in the absence of pain since patients might complain of subjective instability only.