Infraspinatus Muscle
Origin: Infraspinous fossa of the scapula
Insertion: Middle facet of the greater tubercle of the humerus
Actions: External rotation of arm
Innervation: Suprascapular nerve (C5, C6)
Blood Supply: Suprascapular Artery and circumflex humeral artery from the axillary artery
Primary Actions of the Infraspinatus
1. Internal rotation of the arm at the shoulder
1. External rotation of the shoulder
Agonists:
- Teres Minor
- Deltoid (posterior fibers)
Antagonists:
- Subscapularis
- Deltoid (anterior fibers)
- Latissimus Dorsi
- Pectoralis Major
- Teres Major
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Secondary Actions of the Infraspinatus
1. Assists with depression of the humeral head
Agonists:
- Teres Minor
- Subscapularis
Muscle Pain Information: The infraspinatus muscle contributes to pain in the shoulder that descends the arm to the hand. Pain also occurs along the inside edge of the scapula.