肩関節の解剖・機能・臨床的意義――放射線診断に必要な構造理解

The shoulder joint：anatomy, function, and clinical significance：a structural approach to radiologic diagnosis

肩関節は上肢と体幹を連結する運動器の中でも最も可動性に富む関節であり，狭義には上腕骨頭と肩甲骨関節窩から構成される肩甲上腕関節を指す。関節窩の面積は上腕骨頭の軟骨面の約4分の1と小さく，骨性支持は乏しい一方で，人体最大の可動域を有するという特徴をもつ。この高い可動性と引き換えに，肩関節は脱臼や不安定性を生じやすいという二面性を有する^1）。

The shoulder joint is characterized by exceptional mobility achieved through a complex anatomical and functional organization. Rather than functioning as a single joint, shoulder motion is produced by coordinated interactions among multiple anatomical and functional joints, with stability relying predominantly on soft tissue structures rather than osseous support. This review outlines the functional and imaging-oriented anatomy of the shoulder, focusing on the glenohumeral joint, joint capsule, labrum, rotator cuff, rotator interval, long head of the biceps tendon, bursae, and neural structures, with particular reference to their depiction on standard shoulder MRI. Emphasis is placed on understanding the three-dimensional relationships of these components, which is essential for accurate interpretation of diagnostic imaging in radiological practice.