In the literature, some imaging methods have been proposed for diagnosing internal shoulder impingement. Such studies seem to recognize magnetic resonance (MR) imaging and, above all, MR arthrography as the methods of choice for diagnosing glenoid labrum pathologies. However, these methods are not free of risks, are very expensive, and are not easily repeated [3].

Some authors have performed preliminary studies on the use of ultrasonography to display the glenoid labrum by using software and complex devices on large series of patients in everyday clinical practice [4,5].

Herein, we propose that it is possible to identify internal impingement in its early phase by ultrasound examination through a technique that can be easily repeated and follows precautionary therapeutic protocols.

The subject of this study was a professional javelin thrower aged 18, who was right-handed and reported medium-level pain in his right shoulder. His range of motion data was normal, with a Constant scale score of 95/100. The physical findings were a positive sulcus sign and Walch manoeuvre, which suggested a diagnosis of internal impingement.

An ultrasound examination (Esaote Mylab 25 Gold) was performed, with the subject’s arm abducted up to 150° while maintaining its external rotation. The linear probe was positioned in a coronal view from the glenohumeral joint using a rear approach (Supplementary Fig. 1). The results showed the distance between the glenoid cavity and the head of the humerus in its static phase and under stress in full external rotation, considering the dynamics of the head compared to the glenoid cavity.

The examination was performed on both shoulders to make a bilateral comparison of the abovedescribed parameters (Supplementary Fig. 2).

A remarkable portion of the labrum on the affected side appeared hypoechogenic, with a discontinuous profile (Supplementary Fig. 3).

The long head of the biceps did not show alterations when it was examined in transversal and longitudinal views. Such data excluded indirect signs of a SLAP lesion (Supplementary Fig. 4).

Therefore, according to this study, an ultrasound pattern indicative of internal impingement may be characterized by the following findings: a different distance between the head of the humerus and the profile that can be attributed to the glenoid labrum, with a conflict between these two structures; elevation of the humerus in its dynamic phase; altered echogenicity of the area corresponding to the glenoid labrum; and a normal aspect of the long head of the biceps.

We aim to verify this hypothesis by conducting further imaging studies and comparing them with surgical evidence.