In Reply:

The authors would like to thank Dr Martin et al for their interest in our article and for raising this important issue for further discussion. This is a consideration that was acknowledged briefly in the article, but was not explored in depth.

As Dr Martin pointed out, it would be impossible to identify the cases recorded in the registry of those patients intending to undergo staged bilateral total knee arthroplasty (TKA) who either decided against the second procedure or died before undergoing the planned second procedure. However, as far as comparison of the subgroups of staged bilateral cases, this bias can be assumed to be proportional between these groups.