Gamification elements are frequently used in learning environments as a means to engage students and help with the learning process. Adaptive gamification, a more recent approach, attempts to maximize the expected learning objectives by adapting these gamification elements to the needs of each user. In this paper, we present a systematic review of adaptive gamification in educational contexts aiming to understand how these adaptive features work, what they adapt and which strategies they adopt. We identified 16 papers that describe different adaptive gamification strategies for different learning topics, based on factors like user input, user experience, and player typology.