Despite enormous growth in the use of consumer self-tracking devices, the data that many patients collect about their condition is seldom integrated into conversations that take place in the clinic. In this paper we explore the potential roles that self-tracking data could play during clinical interactions between patients with Ankylosing Spondylitis (a chronic rheumatic disease) and their clinicians. We develop a model of the data-centric activities that currently take place within the rheumatology clinic, using field observations, and to discuss how self-tracking data may contribute to each of these activities. We also interview two consultant rheumatologists regarding the opportunities and challenges that the use of self-tracking data may bring. We propose four different roles for self-tracking data in the clinic and discuss possible directions for designing to support these roles.