People in the KM community frequently get tied up in the discussion of tacit and explicit (and don't forget implicit) knowledge. Once you solve this question, you can then spend several hours discussing knowledge in the context of data, information and wisdom. Hierarchy vs. Matrix vs. <something else>. I've gotten lost in these discussions too. Philosophically, these conversations can be interesting. But, in the end the question should be "so what?"
Doug Cornelius tackles this question in Tacit versus Explicit Knowledge
Many knowledge management texts draw a distinction between explicit and tacit knowledge. With one being knowledge in someone's head and the other being knowledge that is written down somewhere. Frankly, I find these terms so abstract that I have forgotten which term is which.
He suggests that we just forget the whole tacit / explicit issue and look at things from the perspective of the people who are asking the questions. Can they find the answers they need? In this context, it doesn't matter what form the "knowledge" takes - if it cannot be found, then it is of no value to the person who needs it. (I have a small quibble with the "by the computer" clause here, but I will let that go.)
And, I think this is the wrong distinction to make. The knowledge is either findable by your computer or it is not findable by your computer.
By finding the knowledge I mean finding the knowledge itself or finding the person who has the knowledge. Certainly all knowledge within a firm is not going to be transferred into a form that is findable by a computer. That is why it is important to identify subject matter experts and make them findable by a computer search.