BackgroundIn the early stages of rheumatic diseases, individuals may present with nonspecific musculoskeletal symptoms (such as arthralgia) in the absence of clinical synovitis. Ultrasound (US) looks potentially helpful, particularly in the absence of symptomatic arthritis. This research aims to study the clinical outcomes of undifferentiated synovitis detected by ultrasound in patients who complain of arthralgia and their predicting factors.ResultsFrom 174 patients with arthralgia, 42% of cases went into remission, and 58% remained as persistent inflammatory arthritis (PIA) (26.4% persisted as undifferentiated arthritis, 31.6% differentiated into specific rheumatic diseases of whom 9.2% became rheumatoid arthritis, 6.3% developed spondyloarthropathy, and other diseases) after 2 years of follow-up. Regression analysis showed that patients with Power Doppler (PD) grade (I or II), grayscale (GS) synovitis grade (II or III), and GS synovitis ≥ grade II in one wrist were significant predictors for PIA in undifferentiated arthralgia’s patients.ConclusionsApproximately 60% of patients with arthralgia developed inflammatory arthritis (IA) after 2 years of follow-up, with 77% of them having US synovitis at the onset of the study. A positive PD signal, grade (II or III) GS synovitis, or ≥ grade II at one wrist were all independently related to the development of PIA in arthralgia patients.