The study of the social construction of knowledge is an important topic in information systems. While the emergence of online social media platforms has brought about multiple new ways of knowledge co-creation by large groups of users, such processes are not yet well understood. We investigate how processes of knowledge co-creation can be studied in online platforms. We utilize data from Wikipedia to explore how knowledge is created and evolves over time. We draw on the theory of social representations (SRT), which views knowledge as a product of collective work carried out by social groups to make sense of their environments. We develop a method for studying social representations on Wikipedia that builds on WikiGen - an analytical tool - and qualitative analysis. Its usefulness is demonstrated with two illustrative case studies, the Cloud Computing and iPad Wikipedia articles. We contribute to IS a new tool and method for studying online knowledge co-creation processes.