The importance of the study of Knowledge Active Forgetting (KAF) is generally described. In this paper, in order to create a comprehensive definition, different definitions of organizational forgetting and knowledge active forgetting presented in the literature, have been reviewed. In addition, key concepts and characteristics that should be considered in the definition of KAF have been extracted. Based on this, concept KAF as an intentional and systematic activity is dependent on the value of knowledge manages. Then, in order to analyze the relationship between KAF and knowledge stickiness to person and organizational context, we gathered qualitative rich data by case study as one of the qualitative research methods. Based on the results of data analysis it can be expressed that by increasing stickiness of knowledge to person and organizational context, the resistance to process of KAF is increased. As a result, organization will be allocated more time and effort in order to manage old and obsolete knowledge. The results of this paper can help managers of organizations to manage their old and obsolete knowledge according to the level of knowledge stickiness to people and organizational context.