What is the likely cause of posterior shoulder pain in this tennis player?
Internal impingement (also known as posterosuperior impingement of the shoulder)
What are the typical MRI features of internal impingement of the shoulder?
Infraspinatus tendinosis and tears, usually superior fibres at the humeral surface. Supraspinatus tendinosis and tear involving the posterior fibres. Posterosuperior labral tear or fraying. Humeral head cysts underlying the infraspinatus tendon.
There are a combination of findings suggestive of internal shoulder impingement consisting of cysts within the humeral head underlying the superior fibres of infraspinatus, undersurface fraying of the superior fibres of infraspinatus, tendinosis and intrasubstance delamination involving the posterior fibres of supraspinatus, and significant fraying of the posterosuperior glenoid labrum.
There is mild thickening of the inferior glenohumeral ligament and anterior joint capsule. Mild subcoracoid and rotator interval oedema is evident. Normal appearance of the coracoacromial ligament. Thickening / increased fluid within the subacromial / subdeltoid bursa. Early superficial chondral wear of the inferior portions of the glenohumeral joint. Mild degenerative hypertrophy of the AC joint with mild capsular hypertrophy and adjacent marrow oedema.