Clinical features

Supraspinatus tendinitis typically affects patients between 40 and 60 years of age following prolonged or excessive use of the shoulder. Pain is usually more severe but of shorter duration in younger patients due to a more vigorous repair process.

Pain is felt in the shoulder and over the deltoid muscle but there is no obvious outward sign of inflammation or swelling. The pain is often worse at night - probably due to muscle spasm after the shoulder muscles relax - and may impede everyday activities such as dressing.

Examination reveals:

• tenderness along the anterior edge of the acromion, most easily elicited with the shoulder in extension. In this position, the supraspinatus tendon is exposed anterior to the acromium process
• pain on active abduction, in a small arc of movement between 60 and 120 degrees - the "painful arc". Movement outside of this arc is painless
• active abduction with the arm held in external rotation throughout is much easier, relatively painless and in this context, virtually pathognomonic of supraspinatus tendinitis
• pain may also be elicited by holding the arm at 90 degrees of flexion and forcibly rotating the shoulder internally
• passive abduction is generally painless as there is no pressure on the tendon

Wasting and weakness of the rotator cuff muscles, and restricted movement, especially of abduction and external rotation, may occur in long standing injury.