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Infraspinatus

The infraspinatus (Latin: musculus infraspinatus) is a flat triangular-shaped muscle of the upper limb. It extends between the scapula and humerus. As the infraspinatus acts at the shoulder joint, it belongs to the muscles of the shoulder girdle. Together with the supraspinatus, teres minor and subscapularis, the infraspinatus muscle is classified as one of the rotator cuff muscles that provide stability to the shoulder joint.

Infraspinatus
OriginInfraspinous fossa of scapula
InsertionGreater tubercle of humerus
Action Shoulder joint stabilization, external rotation of arm
InnervationSuprascapular nerve (C5, C6)
Blood supply Suprascapular and circumflex scapular arteries
Shoulder muscles, Teres major, Supraspinatus, Infraspinatus, Deltoid, Upper extremity, Muscles
Muscles of shoulder region by Anatomy.app

 

Origin

The infraspinatus muscle originates from the infraspinous fossa located on the posterior surface of the scapula.

Upper extremity, upper limb, thorax, muscular system, rotator cuff, infraspinatus, posterolateral view
Infraspinatus (posterolateral view) by Anatomy.app

 

Insertion

The muscle fibers of the infraspinatus pass laterally from the infraspinous fossa and insert on the greater tubercle of the humerus.

Upper extremity, upper limb, muscular system, rotator cuff, infraspinatus, posterior view
Infraspinatus (posterior view) by Anatomy.app

 

Action

The infraspinatus muscle stabilizes the glenohumeral (shoulder) joint and provides external (lateral) rotation of the arm.

Upper extremity, upper limb, thorax, muscular system, rotator cuff, infraspinatus, posterosuperior view
Infraspinatus (posterosuperior view) by Anatomy.app

 

Innervation

The infraspinatus is innervated by the suprascapular nerve that arises from the fifth and sixth cervical (C5, C6) nerve roots of the brachial plexus.

 

Blood supply

The arterial blood supply to the infraspinatus muscle is primarily provided by the suprascapular and circumflex scapular arteries.