Background <p>Shoulder pain is one of the most common musculoskeletal complaints presented to outpatient clinics and may impair daily activities and range of motion. Adhesive capsulitis (AC) has a non-specific clinical presentation that may mimic other causes of a painful shoulder.</p> Aim <p>The aim was to assess the role of ultrasonography (US) in diagnosing adhesive capsulitis in a painful shoulder compared with magnetic resonance imaging (MRI), and to evaluate ultrasound performance for associated shoulder pathologies.</p> Methods <p>This study enrolled 25 adult patients, with a mean age of 46.4 ± 10.7. Cases included 8 males (32%) and 17 females (68%). History taking and assessment of range of motion of the shoulder joint were done, as well as ultrasound and MRI examinations. Clinical positive findings, radiological signs and parameters were recorded. The US diagnosis was correlated and compared with MRI diagnosis.</p> Results <p>The correlation between ultrasound and MRI evaluations demonstrated varying sensitivities, specificities, and diagnostic accuracies in diagnosing different causes of shoulder pain. Ultrasound showed a reasonable diagnostic performance compared to MRI by combination of static parameters including (CHL thickness, ICR thickness… etc.) and dynamic parameters, such as limited abduction and external rotation. Ultrasound can also exclude other conditions of painful stiff shoulder that mimic AC, like bursitis, rotator cuff tendon disease, biceps tendinopathy and acromio-clavicular joint disease.</p> Conclusions <p>Ultrasonography showed promising agreement with MRI for several imaging features and associated shoulder pathologies in this cohort. Given its accessibility and dynamic capability, ultrasound may serve as a first-line imaging modality in patients with painful stiff shoulder with MRI reserved for equivocal cases, while acknowledging operator dependence and the need for standardized measurement protocols and larger confirmatory studies.</p>