The aim of this study was to compare two types of knee arthrodesis. Fourteen patients underwent arthrodesis of the knee in a single institution. Seven had a customised coupled nail (the Mayday arthrodesis nail), and six had external fixation applied, one patient had both procedures undertaken. Twelve patients had infected knee arthroplasty, one had recurrent dislocation following arthroplasty and one had an infected open meniscetomy. Comparison was made with the external fixation in which only two cases achieved bony union compared with all eight (100%) using the customised nail. Time to bony union was also considerably shorter in the later group, as was the length of hospital stay. We conclude that a customised intra-medullary nail is a superior method of knee arthrodesis compared with external fixation.