This paper presents an assessment case study on the evolutionary capability of a large software system using a knowledge-based approach. The knowledge-based assessment is based on interviews with selected stake-holders of a software system. We have used this to assess the capability of the software architecture to evolve in one large Nokia software system. We have found that this approach proves to be effective in large organizations where development teams are distributed in different time-zones, with cultural differences and with limited person-to person communication. The lessons learned and the advantages of using this approach are presented.