Chronic pain entails a large burden of disease and high social costs, but is seldom 'in the picture' and barely understood. Until recently, it was not systematically classified but instead viewed as a symptom or sign. In the new International Classification of Diseases, (ICD)-11, to be implemented in 2022, 'chronic' pain is now classified as a separate disease category and, to a certain extent, approached as a 'disease in its own right'. Reasons that have been given for this are not based so much on new scientific insights, but are rather of pragmatic nature. To explore the background of these recent changes in definition and classification of chronic pain, this paper provides a historical-philosophical analysis. By sketching a brief history of how pain experts have been working on the definition and taxonomy since the 1970s, we demonstrate the various social and practical functions that underlie the new ICD-11 classification of chronic pain. Building on this historical-empirical basis, we discuss philosophical issues regarding defining and classifying chronic pain, in particular performativity and pragmatism, and discuss their implications for the broader philosophical debate on health and disease.