Case-based reasoning posits that learners can use their prior experience to solve new problems. This theory is cited to explain the benefits of problem-based learning (PBL), especially as it relates to knowledge structure development. However, critics argue that learners lack the relevant knowledge structures to simultaneously learn new content and solve complex problems. In terms of learning design, theorists suggest a set of cases (case library) can be used as vicarious memory and thus bridge the experience gap. While this may be beneficial in theory, studies show experts and novices tend to process the details of a case in markedly different ways, which would be problematic in terms of case libraries' ability to scaffolding problem-solving. To address this challenge, this study compared the following conditions in terms of argumentation and knowledge structure development: PBL only, PBL with static case library, PBL with recommendation system case library. Both the case library conditions outperformed the PBL-only condition in terms of initial argument development. However, the PBL with recommendation system case library outperformed the other conditions on rebuttal development. Implications for PBL, CBR, knowledge structure development, and learning design are discussed.