If you are a competent ship's master, what types of knowledge do you need to be able to navigate on a new voyage to an unknown port? You need two types - explicit and tacit, charts and pilots.
But when it comes to entering the narrow congested waters of an unfamiliar foreign port, the ship master's tacit knowledge is not enough, even bolstered by the explicit knowledge in the charts and manuals. Here you need a Pilot.
The economic and environmental risk from today's large cargo ships makes the role of the pilot essential. Pilots possess detailed knowledge of local waterways, and most ports have compulsory pilotage for bog ships. Pilotage is one of the oldest professions, as old as sea travel, and it is one of the most important in maritime safety. The complexities and risks of close navigation make pilotage essential.
Pilotage is an example of deep tacit knowledge which cannot safely be codified, and the master and pilot work together, combining their knowledge of the ship and knowledge of the harbour, to finally berth the ship and end the voyage.
Similarly your knowledge workers need access to two types of knowledge. They need the documented guidance of the "broad areas" of their work, so they can be guided through most of the job. Then they need access (through communities of practice, or subject matter experts) to the deep knowledge of the most risky or complex tasks that can never be made explicit.
Once again, this takes us back to the dual nature of KM - Connect and Collect, Tacit and Explicit. These both need to be components of your Knowledge Management Framework,so that you can take your knowledge workers to the mouth of the harbour, and then to safe anchorage.