Instability of the shoulder joint is evaluated with the use of history, physical examination, radiography, computed tomography or CT-arthrography, fluoroscopy, and examination under general anesthesia. The degree of glenohumeral translation in every direction under general anesthesia is of great value in determining the direction and severity of the instability. Arthroscopy provides a great advantage to inspect the joint clearly and to plan the most appropriate treatment, enabling to draw diagnoses of bone lesions of the humerus and glenoid, labralligamentous lesions, increased capsular volume, biceps pathologies, and rotator cuff tears.