In this paper, we present a novel collaborative authoring tool that was designed to allow medical teachers to formalize and visualize their knowledge for medical intelligent tutoring systems. Our goal is to increase the efficiency and effectiveness in creating the domain model -- often referred to as the bottleneck in developing intelligent tutoring systems. We incorporate the Unified Medical Language System (UMLS) knowledge base to assist the authors in creating the problem solution collaboratively via the videoconferencing platform. The system consists of a share workspace gathering information visualization and tools necessary for collaborative problem-solving tasks. We found that the authoring tool can be used as a standalone program to effectively elicit the knowledge structure of the domain model. This was achieved in hours compared to months for the conventional paper-based approach.