No gold standard test to diagnose FSCS exists.
Diagnosis is based on (i) clinical examination, (ii) exclusion of other pathologies and (iii) normal glenohumeral radiographs. The most simple clinical diagnostic is equal restriction of active and passive glenohumeral external rotation and a normal shoulder radiograph.
Thickening and fibrosis of the rotator interval, destruction and scaring of the subscapular recess, neovascularity, increased cytokine concentrations, contraction of the axillary recess, reduced joint volume, contraction and fibrosis of the coracohumeral ligament, proliferation of fibroblasts and myofibroblasts, presence of contractile proteins, and uncertainty regarding inflammatory changes are commonly reported abnormalities. Adhesions of the capsule to the humeral head do not occur.
Diabetes, family history, possibly hypothyroidism, genetic predispostion and ethnicity have been described as possible risk factors.