The traditional Human Resources model of Knowledge is that knowledge is a human asset held by individuals, and that to bring knowledge to bear on decision, you need to have a knowledgeable individual in the decision making role.
|Shared Knowledge, by Ewa Roskosz, on Flickr|
Knowledge Management, on the other hand, sees the potential to decouple the knowledge from the individual head.
Knowledge can, for example, be held by network of individuals (a community of practice) which collectively holds a level of knowledge which no single individual could emulate. In the KM model it is quite acceptable to refer to collective knowledge, and to say "We know X".
Knowledge can also, where possible, be collected and codified in documented form, where a community of practice codifies and documents some of the simpler and more common knowledge; ideally in a collaborative and evolving setting such as a wiki page. Such resources are not the product of a single person, but of a collective.
Knowledge can also be embedded in process, procedure and structure. When a community of practice is convinced that knowledge is valid, then they can suggest changes to operational processes, structures and roles, to make embed the knowledge in the way the organisation works. Or for a product based organisation, the knowledge becomes embedded in product design, so the product embodies the knowledge of the firm as "the best design we know how to make".
In these three ways knowledge becomes decoupled from the individual, allowing it to be shared with and used by others, and reducing the risk of the loss of knowledge as individuals retire.