Ultrasound Changes in the Enthesis and Peri-enthesis Area of the Patellar and Achilles Tendons in Response to Physical Exercise: Comparison Between Healthy Subjects and Patients with Spondyloarthritis in Clinical Remission.

RATIONALE AND OBJECTIVES: The goal of achieving clinical remission in patients with spondyloarthritis does not necessarily include the resolution of entheseal inflammation from a histological perspective. However, enthesis not clinically inflamed, under mechanical stress, may behave differently from healthy subjects considering the physiopathology of SpA. Our goal was to determine whether ultrasound changes in entheses differ between SpA patients in clinical remission and healthy subjects. METHODS: SpA patients in clinical remission and matched healthy controls were recruited. At baseline, the following variables were measured on the dominant side by ultrasound: thickness of the distal patellar enthesis (hDP), the deep infrapatellar bursa (hDIB), the Achilles enthesis (hA), the preachilleal bursa (hPAB), effusion in the preachileal bursa (hePAB), and the presence of power Doppler signal in both enthesis. All measurements except hDP and hA were collected again after exercise (post-stress ultrasound). RESULTS: 30 patients and 30 controls were enrolled. In all subjects, hDIB, hPAB, and the preachileal bursa occupancy index increased significantly after the exercise. The increase was significantly greater in patients for all variables. At baseline, in patients, hyperemia was detected in one patellar tendon (3.3%) and in two Achilles tendons (6.7%). After exercise, the number of tendons with hyperemia increased to 11/30 (36.7%) and 12/30 (40%), respectively. Among controls, there was no detectable basal hyperemia, but after exercise, it was detected in 1/30 patellar tendons (3.3%) and 2/30 Achilles tendons (6.7%). CONCLUSION: Exercise triggers a greater effusive and hyperemic synovial response in patients in remission than in healthy controls. These findings suggest that the definition of remission should also include an assessment of the synovial response to mechanical stress.