There is limited research considering the usability of medical virtual environments. Usability evaluation is an essential validation phase that considers the extent to which a product achieves its specific goals, with effectiveness, efficiency and satisfaction. A four-stage iterative approach is adopted to enhance usability in the development of a knee arthroscopy training system. This process has drawn attention to issues that may impede system usability for example non-conformity to platform conventions, and visibility of the system status. The process highlights features that computer scientists can overlook when working closely with a system but that are essential to user acceptance and effective application.