A classic line in knowledge management from Polanyi goes, "We know more than we can tell." And David Snowden has enhanced this with, "We can tell more than we can write." And "We only know what we know, when we need to know it."
I just read some discussion at AOK which suggests that maybe the connection between knowing, telling and writing isn't quite so linear. My take on the original sense of the statements above is that they are related to how people exchange knowledge. When I shift this from sharing among people to individual reflection, the processes of writing and telling become much more heavily intertwined: I use the written word as a means to solidify what I think I know. Over time, my personal knowing is enhanced by the writing and the telling - the process of reflection.
I also see, as I write this, that I will leave myself in very murky waters if I go much further. The concept of knowing has many nuances. I'll stop here for now.