The findings are compatible with chronic septic arthritis of the right shoulder joint as well as small subacromion / subdeltoid bursitis.

Synovial enhancement as well as perisynovial edema, and joint effusion are the clue findings for the diagnosis of septic arthritis in the proper clinical setting. 

The differential diagnosis is rheumatoid arthritis (however, it could be an association and predisposing factor as well). Thickened edematous synovium with effusion in patient with chronic articular inflammation is the key diagnostic findings in the proper clinical situation. Erosions are common as well.