agree and disagree,
I will not start the discussion on knowledge as such, for this I refer to the epistemology (cartesian dichotomy between object and subject, knowledge acquisition by emperical study or by deduction, and so on), but in my opinion knowledge can be seen as content in a context, And this is where it should differ from 'pure' IR or Information Management, Knowledge Management is about sharing contextual elements. Since these contextual aspects are quite tacit, we don't know how to handle it. Ergo: tech boys call themselves KM Solutions Providers (bla bla) but in practice only come up with Content Management, old wine in new bags.
So KM vendors segue in 'content management' because they don't know how to facilitate contextual information sharing.
Or when I put it different: knowledge management is achieved through three dimensions: culture, ICT and organisation and the real challenge lies in culture and organisation and not in ICT, so KM tools don't exist.