Clinical assessment systems deployed in rehabilitation settings are likely to consist of several software and hardware components that subjects directly interact with. While it is extremely important that all facets of user interface are tested for critical ergonomic issues, it may be useful to identify those issues during the design and development of the system. In this paper, we present a point-of-care research prototype that is being developed to assist with diagnosis and rehabilitation of upper-limb motor deficits in mild Traumatic Brain Injury (TBI) patients. The aim of this paper is to describe the application of heuristic evaluation to expose user interface problems during the development process. Results from a participatory model of heuristic evaluation are used to highlight the utility of this usability method in clinical engineering especially, in designing medical devices.