Fig. 1

Regions-of-interest (ROIs) in the glenohumeral joint and subacromial space. a Synovium in the glenohumeral joint was divided into 3 ROIs; the anterior, posterior, and inferior synovium. The anterior glenohumeral joint synovium was outlined by the long head of biceps superiorly and by the anterior band of the inferior glenohumeral ligament inferiorly. The inferior glenohumeral joint synovium was defined by the anterior and posterior bands of the inferior glenohumeral ligament. The posterior glenohumeral joint synovium was located by the posterior bands of the inferior glenohumeral ligament inferiorly and by the long head of biceps superiorly. b Synovium in the subacromial space was divided into 4 ROIs; the anterior, posterior, medial, and lateral synovium. The anterior subacromial synovium was outlined by the posterior margin of the coracoacromial ligament laterally and by the base of the coracoid medially. The medial subacromial synovium was defined by the base of the coracoid anteriorly and by the base of the scapular spine posteriorly. The posterior subacromial synovium was located by the base of the scapular spine medially and by the posterolateral angle of the acromion laterally. The lateral subacromial synovium was determined by the posterolateral angle of the acromion posteriorly and the anterior margin of the coracoacromial ligament anteriorly