The supraspinatus muscle primarily acts as an abductor of the humerus, particularly initiating the first 0–15° of motion.
功能： 負責啟動肩關節外展（手臂向外平舉）的最初 15 度，並協助外轉，是穩定肩關節的重要肌肉。
受傷： 由於位於肩峰下方的狹窄空間，是旋轉肌袖中最容易發生肌腱炎、撕裂或因撞擊症候群而受損的肌肉。
Key Details regarding Supraspinatus and Internal Rotation:
Primary Action: Abduction of the humerus.
Rotational Role: Studies indicate the supraspinatus acts as a shoulder internal rotator when the humerus is in a neutral or already internally rotated position.
Anatomy: As part of the rotator cuff, it stabilizes the humeral head in the glenoid fossa.
Functional Testing: The "Empty Can" test (internal rotation with abduction) is often used to isolate the supraspinatus, placing it in a position that tests its strength in that specific orientation
