This paper discusses findings from the introduction and integration of design-led qualitative, research methods into the overall scientific methodology for the design and evaluation of a ‘complex intervention’ through a set of pilot random control trials (RCTs). A set of visualisation tools was co-developed with stakeholders to enhance patient-therapist interaction in the context of the stroke rehabilitation setting. The participative approach recognised the importance of mobilising lay knowledge and experience to drive innovation in the tools whose use helped reduce the ‘social distance’ between therapist, patient and clinical biomechanist. The visualisations aided understanding for patients, enhanced communication between patient and therapist, and provided an objective tool for therapists to monitor progress and communicate this to patients. The implications for service improvement and redesign resulting from involving designers in pilot RCT design are discussed.