Infraspinatus
Shoulder & Scapula · Upper Limb
The Infraspinatus is a Upper Limb muscle within the Shoulder & Scapula group. Originating at Infraspinous fossa of scapula, it inserts at Middle facet of greater tubercle of humerus. It is responsible for several movements: Lateral (external) rotation of arm; stabilizes glenohumeral joint. Innervation is provided by the Suprascapular nerve (C5, C6).
Origin, Insertion, Action & Nerve
Origin
Infraspinous fossa of scapula
Insertion
Middle facet of greater tubercle of humerus
Action
Lateral (external) rotation of arm; stabilizes glenohumeral joint
Nerve
Suprascapular nerve (C5, C6)
Attachments explained
The Infraspinatus is defined first by where it attaches. Its origin is the more fixed anchor, usually the proximal or more stable end that stays put during contraction, while its insertion is the more mobile point that is pulled toward the origin when the muscle shortens.
Origin
Infraspinous fossa of scapula
Insertion
Middle facet of greater tubercle of humerus
Action & function
When the Infraspinatus contracts, it produces the following movements: Lateral (external) rotation of arm; stabilizes glenohumeral joint.
As part of the Shoulder & Scapula group of the Upper Limb, it works alongside neighbouring muscles to generate smooth, coordinated movement and to stabilise the structures it acts on.
Nerve supply & clinical relevance
The Infraspinatus receives its nerve supply from the Suprascapular nerve (C5, C6). This nerve carries fibres from spinal segment(s) C5, C6.
Because a muscle can only contract when its nerve is intact, injury to the Suprascapular nerve or to its spinal roots (C5, C6) can weaken or paralyse the Infraspinatus, impairing the movements it normally produces (lateral (external) rotation of arm). This is why knowing the innervation is central to localising nerve lesions in clinical practice.
How to study the Infraspinatus (the OIANS method)
OIANS stands for Origin, Insertion, Action and Nerve, the four facts that uniquely define every skeletal muscle. To learn the Infraspinatus, work through them in order: picture its origin, trace the muscle to its insertion, reason out the action that shortening between those two points must create, then add the nerve that drives it.
Most students remember the Infraspinatus fastest by linking its action back to its attachments rather than memorising each fact in isolation. Once the origin and insertion make sense, the action usually follows logically.
Infraspinatus quick facts
- Region
- Upper Limb
- Group
- Shoulder & Scapula
- Origin
- Infraspinous fossa of scapula
- Insertion
- Middle facet of greater tubercle of humerus
- Action
- Lateral (external) rotation of arm; stabilizes glenohumeral joint
- Nerve
- Suprascapular nerve (C5, C6)
- Spinal roots
- C5, C6
Frequently asked questions
Where is the Infraspinatus located?
The Infraspinatus is a muscle of the Shoulder & Scapula group, located in the Upper Limb.
What is the origin of the Infraspinatus?
Infraspinous fossa of scapula
What is the insertion of the Infraspinatus?
Middle facet of greater tubercle of humerus
What movements does the Infraspinatus produce?
Lateral (external) rotation of arm; stabilizes glenohumeral joint
What nerve supplies the Infraspinatus?
Suprascapular nerve (C5, C6)
Is the Infraspinatus free to study in OIANS?
Yes. The Infraspinatus is free in OIANS: its full origin, insertion, action and nerve details are open to everyone in the Muscle Directory, and because it belongs to the Upper Limb it is also covered by the free Quiz and Flashcard decks. The other regions, the "All Muscles" deck, and the Progress and Explore tools are unlocked with a one-time Lifetime purchase.
Related muscles
Study the Infraspinatus
Test yourself on Upper Limb muscles with interactive quizzes and flashcards in the free OIANS app.
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