We report a case of early tibial tray fracture of a Duracon knee prosthesis. Aside from the clinical, radiographic, and gross analysis of the failed prosthesis, we also performed analysis on the retrieved polyethylene component and the fractured tibial baseplate. In the analyses, we noted significant femoral component malalignment, uneven tray cementation, and inherent metallurgical weakness. It appears that the high compressive load on the medial tray resulted in bending fatigue failure. To avoid this complication, it is important to restore the normal alignment of the knee joint and use a polyethylene insert of higher conformity, at least 6 mm thick.