Patients with spondyloarthritis, already treated by TNF blocker (adalimumab, etanercept or infliximab), and in stable low disease activity for at least 6 months, will be randomized into 2 groups: either keeping on their usual treatment with stable doses or progressive spacing of injections of their treatment. Follow-up will be done every 3 months during 12 months, with regular monitoring of disease activity and, in patients from the group "spacing", modification of the rhythm of injections according to health state and predefined protocol.