Ultrasound and clinical evaluation of quadricipital tendon enthesitis in patients with psoriatic arthritis and rheumatoid arthritis

Enthesitis is an inflammatory lesion of the tendon, ligament and capsular insertions into the bone, and it is a fundamental element in the diagnosis of spondyloarthropathies. Sonography is the method of choice for studying periarticular soft tissues because it is capable of detecting both the early (oedema, thickening) and the late alterations (erosions and enthesophytes); it is also an inexpensive, biologically harmless and easily repeatable technique. The aim of this study was to compare the prevalence of quadricipital enthesitis in psoriatic arthritis (PsA) and rheumatoid arthritis (RA) patients, and to document any clinical and echostructural differences in this lesion between the two diseases. The results show that enthesitis is more frequent in PsA patients, more than half of whom are asymptomatic. Knee inflammation was found in the PsA patients with enthesitis regardless of the concomitant presence of joint effusion; none of the RA patients suffered from enthesitis alone. Quadricipital enthesitis is more frequent in male patients. There was no significant correlation between the presence of peripatellar psoriatic lesions and enthesitis. Sonographic examinations of patients with enthesitis revealed that those with RA had dominantly inflammatory lesions, whereas PsA patients also showed major new bone deposition.