Ultrasonographic Evaluation of Asymptomatic Shoulder Involvement in Rheumatoid Arthritis: A Prospective Case–Control Study

Background/Objectives: Shoulder involvement is common in rheumatoid arthritis (RA), yet periarticular pathology may remain subclinical. Musculoskeletal ultrasonography enables detection of early inflammatory and structural changes; however, data on asymptomatic shoulder involvement in RA are limited. This study aimed to evaluate ultrasonographic shoulder findings in asymptomatic RA patients, compare them with healthy controls, and assess their association with disease activity. Methods: This prospective case–control study included 31 patients with RA without shoulder pain and 33 asymptomatic healthy controls. Bilateral shoulder examinations were performed using standardized ultrasonographic protocols. Periarticular findings were assessed using the Ultrasound Shoulder Pathology Rating Scale (USPRS), and acromiohumeral distance (AHD) was measured. Disease activity was evaluated using the Disease Activity Score in 28 joints (DAS28). Group comparisons, correlation analyses, receiver operating characteristic (ROC) analysis, and multivariate logistic regression were performed. Results: There were no significant differences in demographic characteristics or comorbidities between groups. Biceps tendinopathy scores were significantly higher in RA patients than in healthy controls (1.0 ± 0.79 vs. 0.5 ± 0.56, p = 0.01), whereas other ultrasonographic parameters, including supraspinatus tendinopathy, dynamic impingement findings, AHD, and total USPRS score, did not differ significantly. DAS28 showed significant positive correlations with biceps tendinosis (r = 0.37, p < 0.05) and supraspinatus tendinosis (r = 0.36, p < 0.05). Total USPRS demonstrated acceptable discrimination for identifying moderate–high disease activity (AUC = 0.73). In multivariate analysis, DAS28 was independently associated with biceps tendinopathy (OR = 1.62, 95% CI: 1.05–2.49). Conclusions: Asymptomatic patients with RA exhibit a higher burden of biceps tendon involvement compared with healthy individuals, and subclinical shoulder ultrasonographic findings are associated with disease activity. Asymptomatic patients with RA demonstrated a significantly higher biceps tendinopathy score compared with healthy controls, whereas most other ultrasonographic parameters, including total USPRS score and AHD, did not differ significantly. These findings suggest that the long head of the biceps tendon may represent a relatively more sensitive site of subclinical periarticular involvement in RA; however, the overall ultrasonographic differences were limited and should be interpreted cautiously.