Infraspinatus Muscle – Attachments, Actions & Innervation

Author: Scott A. Sheffield MS

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The infraspinatus is a thick and triangular muscle. It’s one of the rotator cuff muscles providing the mechanical link between the posterosuperior and anterior parts of the rotator cuff.

image descriptionInfraspinatus Muscle

Image showing superficial muscles of the back and posterior shoulder and arm. Infraspinatus highlighted. Labelled muscles: trapezius, deltoid, infraspinatus, teres major, triceps brachii (lateral head), triceps brachii (long head), latissimus dorsi.
Image showing superficial muscles of the back and posterior shoulder and arm. Infraspinatus highlighted. Labelled muscles: supraspinatus, infraspinatus, teres major, teres minor, triceps brachii (lateral head), triceps brachii (long head).
Image showing superficial muscles of the back and posterior shoulder and arm. Labelled muscle: infraspinatus
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image descriptionAttachments of Infraspinatus :Origin & Insertion

Origin: (proximal attachments)
a. Infraspinous fossa of the scapula.

Insertion: (distal attachments)
a. Middle part of the greater tubercle of the humerus.

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Image showing superficial muscles of the back and posterior shoulder and arm. Infraspinatus highlighted. Labelled muscles: trapezius, deltoid, infraspinatus, teres major, triceps brachii (lateral head), triceps brachii (long head), latissimus dorsi.
Image showing superficial muscles of the back and posterior shoulder and arm. Infraspinatus highlighted. Labelled muscles: supraspinatus, infraspinatus, teres major, teres minor, triceps brachii (lateral head), triceps brachii (long head).
Image showing superficial muscles of the back and posterior shoulder and arm. Labelled muscle: infraspinatus
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Actions of Infraspinatus:

a. image descriptionLaterally rotates the arm at the shoulder (glenohumeral) joint.

b. Helps stablize the shoulder by drawing the humerus toward the glenoid fossa of the scapula.

Innervation of Infraspinatus:

image descriptionNerve to the muscle:
a. Suprascapular nerve.

image descriptionNerve roots:
a. C5 and C6.

Image showing posterior view or suprascapular nerve and infraspinatus.
Image showing the brachial plexus with the suprascapular nerve and roots labelled.
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An Overview of the Posterior Muscles of the Arm:

Test yourself image of posterior view of back and right arm. No labels.
Test yourself image of posterior view of back and right arm. Muscles labelled: trapezius, deltoid, teres major, triceps brachii (lateral head), triceps brachii (long head), latissimus dorsi, extensor carpi radials longus, extensor carpi ulnaris.
Test yourself image of posterior view of back and right arm. Muscles labelled: splenius capitis, rhomboid minor, deltoid, rhomboid major, teres major, triceps brachii (lateral head), triceps brachii (long head), serratus posterior inferior, extensor carpi radials longus, extensor carpi ulnaris.
Test yourself image of posterior view of back and right arm. Muscles labelled: splenius capitis, serratus posterior superior, supraspinatus, infraspinatus, teres minor, teres major, triceps brachii (lateral head), triceps brachii (long head), serratus posterior inferior, extensor carpi radials longus.
Test yourself image of posterior view of back and right arm. Muscles labelled: splenius capitis, splenius crevicis, supraspinatus, infraspinatus, teres minor, teres major, triceps brachii (lateral head), triceps brachii (long head), erector spinae muscles, external oblique, internal oblique.
Test yourself image of posterior view of back and right arm. Muscles labelled: semispinalis capitis, elevator scapulae, supraspinatus, infraspinatus, teres minor, teres major, triceps brachii (lateral head), triceps brachii (long head), erector spinae muscles, external oblique, internal oblique.
Test yourself image of posterior view of back and right arm. Muscles labelled: supraspinatus, infraspinatus, teres minor, teres major, triceps brachii (lateral head), triceps brachii (long head).
Test yourself image of posterior view of back and right arm. Muscles labelled: supraspinatus, infraspinatus, teres minor, teres major.
Test yourself image of posterior view of back and right arm. Muscles labelled: infraspinatus.
Test yourself image of posterior view of back and right arm. Origin and insertion of infraspinatus labelled.
Test yourself image of skeleton of posterior view of back and right arm.
Test yourself while observing the Infraspinatus Muscle
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