| Severe || Exostosis of inferior humerus and/or glenoid measuring more than 7 mm in height as well as [[sclerosis (medicine)|sclerosis]] and narrowing of the joint space (normal joint space is 4–5 mm).<ref>{{cite web|url=http://radref.org/ref.php?id=361|title=Glenohumeral joint space|website=radref.org}}, in turn citing: {{cite journal|last1=Petersson|first1=Claes J.|last2=Redlund-Johnell|first2=Inga|title=Joint Space in Normal Gleno-Humeral Radiographs|journal=Acta Orthopaedica Scandinavica|volume=54|issue=2|year=2009|pages=274–276|issn=0001-6470|doi=10.3109/17453678308996569}}</ref>
|}
==Differential diagnosis==
<gallery>
File:X-ray of rheumatoid arthritis of the shoulder.jpg|Rheumatoid arthritis, also having joint space narrowing, but also periarticular joint erosions (arrows)
</gallery>
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