[Posterior shoulder instability : Epidemiology, examination, and diagnostics]

Posterior shoulder instability (PSI) is rare, accounting for 2-10% of all glenohumeral instabilities, and primarily affects young, physically active patients. Etiologically, traumatic, chronic-repetitive, and atraumatic-habitual forms are distinguished. Clinically, load-dependent posterior shoulder pain predominates, while a subjective feeling of instability is rarely reported. The Jerk and Kim tests are diagnostically decisive, demonstrating high sensitivity and specificity for posteroinferior labral lesions; the modified O'Brien test can provide additional insight. The Stanmore and ABC classifications categorize PSI according to etiology and structural lesions, supporting treatment planning. Imaging diagnostics include radiographs to exclude major structural changes, CT to analyze bony factors such as glenoid retroversion, dysplasia, or bone defects, and MRI to detect typical posterior labral, capsular, and cartilage lesions.