Knowledge of any field is too complex to any individual to cover and therefore they need to interact with colleagues to benefit from stimulation and thus creates a community of practice;

Communities of practice are groups of people who share a passion for something that they know how to do, and who interact regularly in order to learn how to do it better.

To be able to connect the communities of practice with knowledge strategy, Wenger defines three elements.

Domain: the area of knowledge that brings the community together, gives it its identity, and defines the key issues that members need to address. A community of practice is not just a personal network: it is about something. Its identity is defined not just by a task, as it would be for a team, but by an ”area” of knowledge that needs to be explored and developed.

Community: the group of people for whom the domain is relevant, the quality of the relationships among members, and the definition of the boundary between the inside and the outside. A community of practice is not just a web site or a library; it involves people who interact and who develop relationships that enable them to address problems and share knowledge.

Practice: the body of knowledge, methods, tools, stories, cases, documents, which members share and develop together. A community of practice is not merely a community of interest. It brings together practitioners who are involved in doing something. Over time, they accumulate practical knowledge in their domain, which makes a difference to their ability to act individually and collectively.
These three elements in combination are what enable a community of practice to manage knowledge.
Knowledge management is a strategic activity and it starts with strategy and ends with strategy. It connects strategy to performance through knowledge.
The doughnut model should not be seen as a chronological sequence of steps.

The development of communities of practice is a bottom-up process as well as a top-down process. 

Etienne Wenger, Knowledge management as a doughnut: Shaping your knowledge strategy through communities of practice.