Context: Evolution from novice to expert is associated with the development of expert-type knowledge structure. The objectives of this study were to examine reliability and validity of concept sorting (ConSort[C]) as a measure of static knowledge structure and to determine the relationship between concepts in static knowledge structure and concepts used during diagnostic reasoning. Method: ConSort[C] was used to identify static knowledge concepts and analysis of think-aloud protocols was used to identify dynamic knowledge concepts (used during diagnostic reasoning). Intra- and inter-rater reliability, and correlation across cases, were evaluated. Construct validity was evaluated by comparing proportions of nephrologists and students with expert-type knowledge structure. Sensitivity and specificity of static knowledge concepts as a predictor of dynamic knowledge concepts were estimated. Results: Thirteen first-year medical students and 19 nephrologists participated. Intra- and inter-rater agreement for determination of static knowledge concepts were 1.0 and 0.90, respectively. Reliability across cases was 0.45. The proportions of nephrologists and students identified as having expert-type knowledge structure were 82.9% and 55.8%, respectively (p=0.001). Sensitivity and specificity of ConSort[C] in predicting concepts that were used during diagnostic reasoning were 96.8% and 27.8% for nephrologists and 87.2% and 55.1% for students. Conclusions: ConSort[C] is a reliable, valid and sensitive tool for studying static knowledge structure. The applicability of tools that evaluate static knowledge structure should be explored as an addition to existing tools that evaluate dynamic tasks such as diagnostic reasoning.