1. Clinical Perspective

Although historically regarded as an incidental finding, OA may occasionally produce symptoms arising from subacromial impingement or instability at the site of non-union.12-15 Symptomatic OA typically causes pain on palpation of the superior aspect of the acromion, and the diagnosis may be suspected by good clinical response to local injection of analgesics.16 However, such diagnosis is one of exclusion, given the high prevalence of asymptomatic OA and other sources of shoulder discomfort. Radiographs are the mainstay of imaging to detect and classify the OA, but lack accuracy to demonstrate subacromial impingement and instability at the site of non-union.