Sharing knowledge to support clinical work requires more than simple exchange of information. It is reliant on processes that support common perceptions of shared information, and usually occurs within the context of a complex structure of clinical practices that are shaped by both clinical and non-clinical factors. This paper presents a context-aware model for clinical knowledge sharing across organizational and geographical boundaries in e-health. The model draws on activity and situation awareness theories, as well as the belief theory in AI. A primary focus of the model is to enable clinicians in disparate locations to gain a common representation of relevant situational information in each other's work contexts based on the notion of clinical work practice. We describe the conceptual design of the model and explore an example use case illustrating how the approach can facilitate practice-centred clinical knowledge sharing across geographical boundaries.