Section 01 of 20
Introduction
Infraspinatus is a thick, triangular muscle that fills most of the infraspinous fossa — the broad depression on the back of the shoulder blade below the scapular spine. It is one of the four rotator cuff muscles (along with supraspinatus, teres minor, and subscapularis), often remembered with the acronym SITS.
Infraspinatus is the primary external (lateral) rotator of the shoulder and, like the other rotator cuff muscles, plays an important role in keeping the head of the humerus centered and stable in the glenoid fossa during arm movement, rather than only producing large, visible motions.
For massage therapists, infraspinatus is one of the most clinically relevant muscles in the entire body, both because of how often it becomes tight or tender in clients with rounded-shoulder posture or repetitive overhead activity, and because of its well-documented referred pain relationships.
Section 02 of 20
Origin
| Origin | Infraspinous fossa of the scapula — the broad bony depression below the spine of the scapula, on the posterior surface of the shoulder blade. |
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An anatomical image for this section will be added when verified source media becomes available.
Section 03 of 20
Insertion
| Insertion | Middle facet of the greater tubercle of the humerus (posterior facet), with fibers blending into the posterior aspect of the shoulder joint capsule. |
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An anatomical image for this section will be added when verified source media becomes available.
Section 04 of 20
Actions
| Primary action | External (lateral) rotation of the shoulder. |
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| Secondary actions | Stabilizes the humeral head in the glenoid; the upper fibers assist abduction and the lower fibers assist extension and adduction. |
| Movement at the joint | Glenohumeral (shoulder) joint. |
| Heads / fiber groups | Single muscle with upper (transverse) and lower (oblique) fiber groups. |
| Functional examples | Throwing; reaching behind the head; brushing the hair; serving in tennis; turning the arm outward. |
Primary actions
- External (lateral) rotation of the shoulder — infraspinatus is generally considered the primary external rotator, assisted by teres minor.
Secondary / functional role
- Along with the other rotator cuff muscles, helps dynamically stabilize the humeral head within the glenoid fossa during arm movement, resisting excessive anterior or superior translation of the humeral head depending on arm position.
- Assists in horizontal abduction of the shoulder when the arm is elevated.
Section 05 of 20
Nerve Innervation
| Nerve | Suprascapular nerve |
|---|---|
| Roots | C5, C6 |
| Relationship | The suprascapular nerve arises from the upper trunk of the brachial plexus, passes through the suprascapular notch (deep to the transverse scapular ligament) to first supply supraspinatus, then continues around the lateral border of the scapular spine through the spinoglenoid notch to reach infraspinatus. Both notches are recognized potential sites of nerve compression. |
Section 06 of 20
Blood Supply
Infraspinatus is primarily supplied by the suprascapular artery, with additional contribution from the circumflex scapular artery (a branch of the subscapular artery), both of which participate in the rich anastomotic network around the scapula.
Section 07 of 20
Pictures and Visual Anatomy
An anatomical image for this section will be added when verified source media becomes available.
Section 08 of 20
Functional Movement
Infraspinatus turns the arm outward and holds the humeral head centered in the shoulder socket during almost every arm movement. Examples include throwing, reaching behind the head, brushing hair, serving in tennis, and lifting overhead.
Section 09 of 20
Synergists and Antagonists
Synergists
Teres minor (external rotation); posterior deltoid (horizontal abduction).
Antagonists
Subscapularis (internal rotation) is the primary antagonist; pectoralis major and latissimus dorsi also contribute internal rotation force opposing infraspinatus.
Section 10 of 20
Palpation and Location
Client position
Client prone or side-lying, arm relaxed, scapula accessible.
Landmarks and technique
- Locate the spine of the scapula, then move inferior to it — infraspinatus fills the broad fossa below the spine, extending down toward the inferior angle and out toward the lateral border of the scapula.
- Asking the client to gently externally rotate the arm (with the elbow bent and tucked at the side) will help the therapist feel the muscle contract, distinguishing it from the surrounding fascia and teres minor/major along the lateral border.
- Teres minor lies along the upper lateral border of the scapula, just inferior to infraspinatus's lateral portion, and teres major lies further inferior still — palpating during resisted external rotation versus resisted adduction/internal rotation can help differentiate these neighboring muscles.
- The muscle is broad and relatively superficial in the fossa, making it comfortable to palpate with moderate, well-distributed pressure in most clients.
Section 11 of 20
Massage Therapy Relevance
Infraspinatus is one of the most frequently tight and tender muscles seen in massage therapy practice. Clients with rounded-shoulder, forward-head posture often develop lengthened but overworked and tender posterior cuff muscles, including infraspinatus, as they work to control the head of the humerus and stabilize the shoulder blade against the pull of tighter anterior structures.
Repetitive overhead activity (throwing sports, swimming, racquet sports, manual labor) places high demand on infraspinatus both for rotation and for its stabilizing role, and it is commonly implicated in overuse patterns among these populations.
Infraspinatus is also one of the most well-documented sources of referred shoulder pain in massage-therapy and myofascial trigger point literature, discussed further below.
Section 12 of 20
Dysfunction: What Happens When Movement Goes Wrong
Changes in how a muscle works can change how a joint moves. The points below describe possibilities that may be associated with altered muscle function; they are not diagnoses, and one muscle is never assumed to be the sole cause of a problem.
When the muscle is weak
Weakness may reduce external rotation strength and may allow the humeral head to move forward or upward, which may be associated with shoulder pain and reduced overhead function.
When it is tight or shortened
Tightness may be associated with limited internal rotation and reaching behind the back and may contribute to posterior shoulder tension.
When it is overused
Throwing, swimming, and overhead work may overload the muscle and may contribute to a deep ache at the back of the shoulder.
When it is strained
A strain or tendinopathy may cause pain with resisted external rotation; rotator cuff tears, neck problems, and other shoulder conditions can look similar.
When it is inhibited or others compensate
Reduced activation may be associated with more work by the deltoid and upper trapezius and a shrugging pattern during arm elevation.
When it does not coordinate well with synergists and antagonists
Poor balance with subscapularis and the rest of the rotator cuff may alter humeral head control and may be associated with subacromial pain.
Section 13 of 20
Conditions, Pathologies, and Pain Relationships
Rotator cuff tendinopathy
What it is: Irritation or degenerative change of the infraspinatus tendon (or other cuff tendons) near its insertion on the greater tubercle.
Why the muscle may be involved: Repetitive rotational loading and, in some cases, overlapping subacromial impingement can irritate the tendon.
Typical symptoms: Posterior/lateral shoulder pain, often worse with resisted external rotation or overhead activity.
Similar-presenting conditions: Supraspinatus tendinopathy, subacromial bursitis, glenohumeral joint pathology.
Refer when: Pain is persistent, significantly limits function, or is associated with notable weakness.
Rotator cuff tear (partial or full-thickness)
What it is: A structural tear of the infraspinatus tendon (or adjacent cuff tendons), which can occur acutely from trauma or develop gradually with age-related degeneration.
Why the muscle may be involved: The insertion area is subject to cumulative mechanical stress and reduced blood supply in some individuals with age.
Typical symptoms: Weakness in external rotation, pain with movement or at rest, and sometimes an inability to actively hold the arm in certain positions.
Similar-presenting conditions: Tendinopathy without tear, suprascapular nerve entrapment, cervical radiculopathy.
Refer when: Any suspected tear (significant weakness, especially after trauma, or an inability to actively maintain arm position) warrants medical/orthopedic evaluation rather than massage treatment alone.
Suprascapular nerve entrapment
What it is: Compression or irritation of the suprascapular nerve, most often at the suprascapular notch or the spinoglenoid notch.
Why the muscle may be involved: This nerve directly supplies infraspinatus (and supraspinatus); entrapment can cause weakness and pain referable to the posterior shoulder.
Typical symptoms: Deep, poorly localized posterior shoulder pain, weakness in external rotation, and in longer-standing cases visible atrophy of the infraspinatus fossa.
Similar-presenting conditions: Rotator cuff tear, cervical radiculopathy, brachial plexus pathology.
Refer when: Suspected nerve entrapment (especially with visible muscle atrophy or progressive weakness) should be referred for medical/neurological evaluation.
Myofascial trigger points and referred pain
What it is: Localized hyperirritable spots within the muscle associated, in massage-therapy and myofascial literature, with characteristic referred pain patterns.
Why the muscle may be involved: Infraspinatus is one of the most frequently cited sources of referred shoulder pain in this literature.
Typical symptoms: Deep aching in the anterior and lateral shoulder, sometimes extending down the arm, that can mimic other shoulder or cervical conditions.
Similar-presenting conditions: Rotator cuff pathology, cervical radiculopathy, glenohumeral joint pathology — referred pain patterns are a useful clinical clue, not a definitive diagnostic tool.
Refer when: Symptoms are severe, persistent, associated with neurological signs, or do not respond to conservative care.
Section 14 of 20
Example Clinical Relationship
Why infraspinatus pain often "shows up" somewhere else
Infraspinatus is one of the most commonly discussed muscles in myofascial referred-pain literature, with described referral extending into the anterior shoulder, deep into the glenohumeral joint region, and sometimes down the lateral arm and forearm. This is clinically important because a client describing anterior shoulder or arm discomfort may actually have a posterior cuff (infraspinatus) origin for that sensation, rather than a problem localized to where the pain is felt.
This referred-pain relationship is a useful piece of clinical reasoning for massage therapists, but it should not be treated as a diagnostic certainty. Referred pain patterns described in massage-therapy and trigger-point sources are based on clinical observation and vary in the quality of supporting evidence; anterior or lateral arm/shoulder pain can also arise from rotator cuff pathology, cervical spine pathology, or other regional structures. Within scope, therapists can use this relationship to guide assessment and treatment planning (for example, considering infraspinatus even when a client points to the front of the shoulder), while avoiding diagnostic claims and referring out when symptoms are severe, persistent, or accompanied by neurological signs.
Section 15 of 20
Massage and Treatment Approaches
The following approaches may be considered for a generally healthy client with no contraindications present.
Broad warming strokes
Why: Prepares the tissue over the broad infraspinous fossa and allows tone assessment.
Direction/location: Broad strokes across the posterior scapula, from the medial border out toward the humerus.
Pressure: Light to moderate.
Compression and kneading
Why: The broad, relatively superficial fossa is generally well suited to sustained compression and kneading to address common tightness.
Direction/location: Through the body of the muscle within the infraspinous fossa.
Pressure: Moderate to firm, as tolerated — this area generally accommodates more direct pressure than many other shoulder muscles, but should still be guided by client feedback.
Stripping and friction
Why: Can address fiber-direction tension and, when appropriate and within training, localized tenderness near the musculotendinous junction.
Direction/location: Along fiber direction from the scapular border toward the greater tubercle insertion; friction techniques, if used, are typically localized to a specific tender point.
Pressure: Moderate, progressing gradually.
Avoid: Aggressive friction directly over a suspected acute tear or highly irritable/inflamed tissue.
Gentle stretching and passive/active movement
Why: May help address tightness and support general range of motion.
Direction/location: Gentle internal rotation (hand-behind-back or across-body internal rotation stretch) performed slowly and within comfortable range.
Pressure: Gentle; avoid forcing end range, especially in clients with any shoulder instability history.
Reciprocal inhibition / muscle-energy-style approaches
Why: Light resisted external rotation followed by relaxation and gentle internal rotation stretch can be used within general massage-therapy scope to support comfortable range of motion.
Pressure: Light resistance only.
Section 16 of 20
Precautions and Contraindications
Use caution or avoid the area when any of the following are present
- Acute shoulder injury or suspected rotator cuff tear.
- Recent shoulder surgery without medical clearance for massage.
- Unexplained swelling, significant weakness, or visible muscle atrophy in the infraspinous fossa.
- Signs of acute inflammation or infection.
- Suspected suprascapular nerve entrapment or other nerve-related symptoms.
- Significant recent trauma to the shoulder region.
Vulnerable structures — general awareness
- The suprascapular and spinoglenoid notches (superior/lateral scapular border region) where the suprascapular nerve and vessels pass — avoid aggressive sustained pressure directly at these specific notch locations.
- Adjust pressure over any area the client identifies as unusually tender or that appears visibly atrophied.
Section 17 of 20
Red Flags and When to Refer
Postpone massage and refer for medical evaluation if a client reports or shows:
- Sudden significant weakness in rotating the arm outward, especially after trauma.
- Visible muscle wasting/atrophy in the infraspinous fossa.
- Numbness, tingling, or other neurological symptoms in the shoulder or arm.
- Signs of infection (fever, redness, warmth, swelling).
- Unexplained, severe, or worsening pain not clearly related to a specific movement or activity.
- Recent significant shoulder trauma or suspected dislocation/fracture.
Section 18 of 20
Study Summary
Infraspinous fossa of the scapula.
Middle facet of the greater tubercle of the humerus.
External (lateral) rotation of the shoulder; dynamic stabilization of the humeral head.
Suprascapular nerve (C5, C6).
Frequent site of tightness and tenderness; well-documented referred pain into the anterior/lateral shoulder and arm; core rotator cuff stabilizer.
Section 19 of 20
Instructor Narration
Open narration script (readable / for audio conversion)
Section 20 of 20