Thin-slice 3D MR arthrographic analysis of capsular folds and fold-like structures in the superior shoulder joint

Background Superior capsular folds and fold-like structures in the glenohumeral joint are potential sources of superior shoulder POS=12ptpain. Purpose To obtain detailed information about the arthrographic anatomy and morphology of superior capsular folds and fold-like structures. Material and Methods This study followed a retrospective design and involved 300 consecutive shoulder magnetic resonance (MR) images and MR arthrograms in two centers. The origins and insertions of the superior capsular folds and fold-like structures in the glenohumeral joints were carefully examined and documented. Four subtypes of extensions in the sagittal-oblique plane of the posterior synovial fold were identified from the MR arthrograms, according to their associations with the biceps tendon long head, superior glenoid notch, and supraspinatus tendon. Further, two morphological subtypes of superior synovial folds were identified: cord-shaped and fan-shaped. Results Superior capsular folds and fold-like structures in the shoulder joint were identified in 11 (4%) patients. Of these 11 superior capsular folds, 6 (54.5%) were then confirmed upon arthroscopy. The cord-shaped type was the most common MR arthrographic superior synovial fold and was detected in 8/11 (72.7%) patients. Type B was the most common form according to the course and insertion of the superior capsular fold (4/11 [37%] patients). Conclusion Superior capsular folds, probably normal capsular anatomical variants, tend to be present in the posterior portions of the superior shoulder joint capsule and are rarely seen in MR arthrograms. These anatomical variations tend to be symptomatic, especially in young individuals. © The Foundation Acta Radiologica 2026