Development and Validation of Clinical Diagnostic Tests for Stage I and II Idiopathic Frozen Shoulder Using MRI Features of the Rotator Interval

Idiopathic frozen shoulder (IFS) is a common musculoskeletal condition characterized by pain and restricted shoulder motion. Accurate diagnosis in the early stages remains difficult due to the absence of validated, anatomically grounded clinical tests. Existing bedside assessments such as the Coracoid Pain Test (CPT), Direct Tenderness Palpation of External Rotation (DTPER), and External Rotation Positional Test (ERPT) show promise but have not been validated against imaging.

Magnetic resonance imaging (MRI) is capable of detecting key rotator interval (RI) changes in IFS, including coracohumeral ligament thickening and anterior capsule fibrosis, but its cost and limited accessibility make it impractical for routine screening.

This cross-sectional diagnostic study aims to develop and validate the Coracoid Pain Test Scale (CPTS) and evaluate its reliability and diagnostic accuracy, along with DTPER and ERPT, using MRI findings of the rotator interval as the anatomical reference standard. Adult participants with Stage I and II IFS will be assessed, with inclusion and exclusion criteria applied to minimize confounding conditions. The primary outcome will be the diagnostic accuracy of CPTS compared with MRI. Findings are expected to provide clinicians with a standardized, reliable, and cost-effective tool for early diagnosis of frozen shoulder, reducing unnecessary imaging referrals and supporting timely, evidence-based management.