With the massive spread of Internet use, the accessibility of user interfaces (UI) is an ever more pressing need. Much work has been developed on this subject in order to define generic or situational accessibility recommendations and to propose tools for user interface adaptation. However, difficulties remain, particularly related to the complexity of possible contexts of use, such as the multiplicity of characteristics of the context of use, the imprecision of the values assigned to these characteristics and the combination of multiple adaptation rules. This article shows how a dynamic adaptation engine based on fuzzy logic can be used to implement accessibility recommendations. We show how this approach makes it possible to overcome these difficulties through fuzzy logic with the capacity to manage combinatorial rules, making it possible to take into account potentially complex contexts of use. This approach is illustrated with a concrete example.