Learning scientists have indicated that one way to support knowledge construction in asynchronous threaded discussions is to provide means by which critical discourse can be supported. However, studies that seek to understand critical discourse in online learning tend to focus on the outcomes of threads or examine threads in aggregate. In order to understand the pedagogical processes by which knowledge construction can be initiated and sustained, I examined patterns of social, cognitive, and teaching presences influencing the development of pivotal notes (notes that trigger knowledge construction). Evidence suggests that exhibiting high levels of cognitive presence tends to lead quickly to knowledge construction, whereas the other presences do not. Research directions are suggested to better understand these processes.