Spondylarthropathies (SpA) are among the most common chronic inflammatory rheumatisms in adults, responsible for a muscular loss or sarcopenia which can be very disabling, not much documented in the literature, and not yet studied in France. In addition, sarcopenia is associated with decreased physical activity and increased risk of falls and fractures. A better characterization of the determinants of this muscular loss will allow to better detect and take care of it.

The aim is to conduct the first French study on the prevalence and severity of sarcopenia in patients with spondyloarthropathies and to study the variables that may be associated with it. Finally, we propose to evaluate obesity related to sarcopenia in these patients and compare them to cases matched for age and sex (from OFELY / STRAMBO cohorts, Lyon, FRANCE).

This is a prospective interventional and monocentric study with minimal risks and constraints: patients will be included for one day for an evaluation of their sarcopenia by measuring their muscle strength, physical performance and body composition and recording of their socio-demographic and disease characteristics.

Inclusion Criteria:

• Men and women, 18 to 80 years old
• Hospitalized or attending the rheumatology department for spondyloarthopathy.

Exclusion Criteria:

• no signed consent
• Immobilization for a period of more than 15 days during the last 3 months
• pregnant or breastfeeding woman
• Not affiliated to the national healthcare insurance
• difficulty in understanding French
• psychiatric disorder