In this paper we propose a knowledge-based approach for the support of adaptive and context-aware behavior in multi-agent systems. We identify the agents knowledge which is present in a system as a central factor for context-awareness and for the systems ability to adapt to changing environments. We provide a framework which supports simple and intuitive specification of complex knowledge configurations. We discuss the semantics and formal backgrounds of the central notion of knowledge conformance. Finally we describe an algorithm for reasoning about knowledge conformance, i.e. for deciding whether a knowledge specification holds for an agent (or a group of agents). Our algorithm heavily relies on the features from membrane computing and is especially well-suited for reasoning about incomplete knowledge. In addition it supports the incremental introduction of situational knowledge and thus supports the dynamics of context-awareness.