Infraspinatus Muscle: Anatomy, Function, Pain Causes, and Exercises

The Infraspinatus Muscle is one of the four muscles of the rotator cuff. Located on the back of the shoulder blade, it helps rotate the upper arm outward and keeps the shoulder joint stable during lifting, reaching, throwing, and overhead activity.

Pain at the back of the shoulder, weakness while rotating the arm outward, or discomfort after repetitive overhead movement can involve the infraspinatus. However, similar symptoms may also come from other rotator cuff muscles, the shoulder joint, or nerves in the neck. A proper clinical assessment matters when symptoms persist or affect normal function.

Infraspinatus at a Glance

Attribute	Detail
Origin	Infraspinous fossa of the scapula (shoulder blade)
Insertion	Middle facet of the greater tuberosity of the humerus
Primary action	External, or lateral, rotation of the shoulder
Secondary role	Stabilizes the humeral head in the glenoid cavity
Innervation	Suprascapular nerve, mainly C5–C6 nerve roots
Blood supply	Primarily the suprascapular and circumflex scapular arteries
Rotator cuff group	Supraspinatus, infraspinatus, teres minor, and subscapularis

What Is the Infraspinatus?

The infraspinatus is a broad, triangular muscle on the posterior surface of the scapula. It occupies most of the infraspinous fossa, the shallow hollow below the bony spine of the shoulder blade.

It is one of four muscles that make up the rotator cuff:

• Supraspinatus
• Infraspinatus
• Teres minor
• Subscapularis

Together, these muscles help centre the head of the humerus in the glenoid, commonly called the shoulder socket. This control is especially important during overhead movements, when the larger deltoid muscle pulls the arm upward.

The infraspinatus is best known for external rotation: the motion of turning the upper arm away from the body. For example, it contributes when you reach back to put on a jacket, bring your hand behind your head, throw a ball, or pull a seatbelt across your body.

Infraspinatus Origin, Insertion, Action, and Innervation

The following quick anatomy facts answer the most common questions about the infraspinatus muscle.

Origin

The infraspinatus originates mainly from the infraspinous fossa of the scapula. Some fibers also arise from the tough fascia covering the muscle.

Insertion

Its tendon passes across the back of the shoulder joint and attaches to the middle facet of the greater tuberosity of the humerus. The greater tuberosity is the prominent bony area on the upper outer part of the arm bone.

Action

The primary action of the infraspinatus is external rotation of the shoulder. It also contributes to shoulder stability by helping hold the humeral head against the glenoid cavity during arm movement.

Innervation

The suprascapular nerve supplies the infraspinatus. This nerve mainly comes from the C5 and C6 nerve roots of the brachial plexus.

Blood Supply

The infraspinatus receives blood mainly from branches of the suprascapular artery and circumflex scapular artery.

What Does the Infraspinatus Do?

The infraspinatus has two key jobs: it externally rotates the shoulder and supports shoulder stability.

External Rotation of the Shoulder

External rotation moves the upper arm away from the body. Imagine standing with your elbows bent to 90 degrees and tucked near your ribs. Rotating your forearms outward activates the infraspinatus.

This motion is important in daily tasks and sport. It is used in throwing, swimming, serving in tennis, lifting objects, reaching behind the body, and controlling the arm during overhead activity.

Shoulder Joint Stability

The shoulder is designed for mobility, but that mobility comes with less inherent stability than a deeper ball-and-socket joint such as the hip. The infraspinatus helps solve that problem by keeping the humeral head centred in the glenoid while the arm moves.

During arm elevation, the deltoid produces an upward pull on the humerus. The rotator cuff, including the infraspinatus, provides a stabilizing force that helps maintain efficient shoulder movement.

The Infraspinatus Tendon

The infraspinatus muscle narrows into a flat tendon near the shoulder joint. This tendon blends with the posterior part of the shoulder capsule before attaching to the greater tuberosity of the humerus.

The tendon is an important part of the rotator cuff. It transfers force from the muscle to the upper arm bone, enabling external rotation and helping maintain shoulder stability.

Like other rotator cuff tendons, the infraspinatus tendon can become irritated, degenerative, or torn. Symptoms from tendon problems can overlap with pain arising from the supraspinatus, teres minor, labrum, biceps tendon, neck, or shoulder joint itself. Shoulder pain should not automatically be diagnosed as an infraspinatus injury.

Infraspinatus Tendinopathy

Tendinopathy refers to tendon irritation and structural change that may develop after repeated loading over time. Repetitive overhead activity, poor shoulder mechanics, sudden increases in training load, and age-related tendon changes can contribute.

Infraspinatus tendinopathy may cause:

• A dull ache at the back or outer part of the shoulder
• Pain during external rotation or overhead activity
• Discomfort while lying on the affected shoulder
• Reduced tolerance for throwing, lifting, or swimming
• Mild weakness caused by pain inhibition

Infraspinatus Tendon Tears

A tear can involve part of the tendon thickness or extend through its full thickness.

• A partial-thickness tear damages some tendon fibers but does not fully detach the tendon from bone.
• A full-thickness tear extends through the tendon and may detach it from its attachment site.

Tears may result from an acute injury, such as a fall, but they may also develop gradually through long-term tendon degeneration. Infraspinatus tears often occur alongside tears or degeneration in other rotator cuff tendons rather than as completely isolated injuries.

Infraspinatus vs. Teres Minor

The infraspinatus and teres minor are close neighbours on the back of the shoulder blade. Both contribute to external rotation, so they are often discussed together. They are not identical, however.

Feature	Infraspinatus	Teres Minor
Size	Larger	Smaller
Main location	Broad infraspinous fossa of the scapula	Lateral border of the scapula, below the infraspinatus
Main action	External rotation and shoulder stability	External rotation and shoulder stability
Nerve supply	Suprascapular nerve	Axillary nerve
Clinical relevance	Weakness may occur with suprascapular nerve compression	Weakness may occur with axillary nerve injury

The infraspinatus usually makes the larger contribution to external rotation strength. Because the muscles have different nerve supplies, selective weakness can help clinicians identify a possible nerve-related problem.

Common Causes of Infraspinatus Pain

Infraspinatus-area pain can arise from the muscle, tendon, shoulder joint, or nearby nerves. Common causes include overuse, tendon degeneration, rotator cuff tears, strain, and nerve compression.

Repetitive Overhead Use

Repeated throwing, swimming, serving, painting, lifting, or manual work can overload the rotator cuff. A sudden rise in activity volume or intensity may irritate the tendon or muscle.

Rotator Cuff Tendinopathy

Tendinopathy develops when a tendon has difficulty tolerating repeated load. It can be associated with pain during external rotation, reaching overhead, and sport-specific movements.

Muscle Strain

An infraspinatus strain may occur after sudden force, an awkward lift, an unexpected pull, or a rapid increase in exercise intensity. Strains affect muscle fibers rather than the tendon itself.

Partial or Full-Thickness Tear

Rotator cuff tears can occur after trauma or gradually over time. A tear may cause weakness, reduced endurance, pain with activity, night discomfort, or difficulty lifting the arm. Not every tear is painful, so a noticeable loss of external rotation strength should be assessed.

Suprascapular Nerve Compression

The suprascapular nerve supplies the infraspinatus. Compression near the spinoglenoid notch can produce isolated infraspinatus weakness or muscle wasting. In some cases, a ganglion cyst or repetitive traction in overhead athletes may be involved.

Referred Pain

Pain felt near the infraspinatus is not always caused by the muscle or tendon. The cervical spine, shoulder joint, other rotator cuff structures, or nerve irritation can produce overlapping symptoms.

Infraspinatus Pain Symptoms

Symptoms depend on the exact cause and severity of the problem. Common signs include:

• A deep, aching sensation at the back or outer part of the shoulder
• Pain during overhead reaching, throwing, swimming, or lifting
• Weakness when rotating the arm outward
• Reduced endurance with repetitive shoulder activity
• Pain while lying on the affected shoulder
• Difficulty reaching behind the back
• Stiffness or reduced shoulder range of motion
• Clicking, catching, or grinding during movement

An acute injury may cause sudden pain and weakness. Degenerative tendon problems usually develop more gradually. A tear can sometimes produce little pain but noticeable weakness.

When to See a Doctor

Seek assessment from a qualified healthcare professional if shoulder pain:

• Follows a fall, collision, dislocation, or other significant injury
• Causes clear weakness or loss of shoulder function
• Prevents you from lifting, reaching, working, or sleeping normally
• Continues despite reducing aggravating activities
• Includes visible muscle wasting around the back of the shoulder
• Is associated with numbness, tingling, neck pain, fever, swelling, or unexplained symptoms

Sudden inability to raise the arm, deformity after injury, severe swelling, or signs of infection require urgent medical attention.

A clinician may assess shoulder motion and strength, including resisted external rotation. Ultrasound or magnetic resonance imaging (MRI) may be used when a tendon tear, significant muscle injury, or other structural problem is suspected.

How Infraspinatus Problems Are Diagnosed

Diagnosis begins with a medical history and physical examination. A clinician will consider where the pain occurs, how it began, whether there was trauma, which activities aggravate symptoms, and whether weakness or nerve symptoms are present.

Physical Examination

A clinician may test:

• Active and passive shoulder range of motion
• Strength during external rotation
• Pain during resisted movement
• Rotator cuff function
• Scapular control
• Neck motion and nerve-related symptoms

Resisted external rotation with the elbows near the sides is commonly used to assess infraspinatus function. Pain or weakness may suggest a rotator cuff or nerve-related issue, but no single test can confirm a diagnosis on its own.

Imaging

Imaging is not needed for every case of shoulder pain. When needed, options may include:

• X-ray: Helps evaluate bone changes, arthritis, fractures, and some causes of shoulder impingement
• Ultrasound: Can assess many rotator cuff tears dynamically and without radiation
• Magnetic resonance imaging (MRI): Provides detailed information about tendons, muscle quality, fluid, labrum, and other soft tissues

Infraspinatus Treatment Options

Treatment depends on the diagnosis, tear size, functional demands, duration of symptoms, activity level, and overall shoulder condition. Many shoulder and rotator cuff problems can be managed without surgery, particularly when symptoms are mild or moderate and there is no major functional deficit.

Activity Modification and Pain Management

Initial management may include temporarily reducing activities that trigger symptoms, especially repetitive throwing, overhead lifting, or heavy pulling movements. This does not necessarily mean complete rest. Pain-free or low-pain movement is often useful for maintaining mobility.

Ice may help some people manage short-term pain after activity. Nonsteroidal anti-inflammatory drugs (NSAIDs) may be appropriate for some patients, but they are not suitable for everyone. Speak with a pharmacist or healthcare professional if you have kidney disease, stomach ulcers, cardiovascular disease, take blood thinners, or are unsure whether these medicines are safe for you.

Physical Therapy

Physical therapy is often central to treatment. A programme may include:

• Gradual external-rotation strengthening
• Scapular stabilisation work
• Shoulder mobility exercises
• Thoracic spine mobility where relevant
• Progressive loading for the rotator cuff
• Sport- or work-specific return-to-activity planning

The goal is not simply to strengthen one muscle. Effective rehabilitation usually improves the coordination and capacity of the whole shoulder complex.

Injections and Other Treatments

Some people with persistent pain may discuss an injection with a qualified clinician. The American Academy of Orthopaedic Surgeons (AAOS) 2025 clinical practice guideline states that a single corticosteroid injection with local anaesthetic may provide short-term improvements in pain and function for some rotator cuff conditions.

The choice of injection, timing, and potential risks should be discussed individually. An injection does not repair a torn tendon and should not replace a rehabilitation plan when exercise-based management is appropriate.

Surgery

Surgery may be considered for selected full-thickness tears, acute traumatic tears, significant weakness, ongoing functional limitation, or symptoms that do not improve after an appropriate trial of non-surgical treatment.

Surgical decisions are individual. Tear size, tendon retraction, muscle quality, age, occupation, sports demands, and personal goals all matter. An orthopedic shoulder specialist can explain the likely benefits, limitations, and risks in a specific case.

Infraspinatus Exercises

Exercises can help build external rotation strength and shoulder control, but they should not be used to self-treat a suspected acute tear, fracture, dislocation, or severe nerve problem. If an exercise causes sharp pain, worsening pain, or significant weakness, stop and seek professional guidance.

Start with light resistance, controlled repetitions, and a pain-tolerable range. The aim is controlled rotator cuff loading, not heavy weight.

Side-Lying External Rotation

1. Lie on your unaffected side with the painful arm on top.
2. Bend the top elbow to 90 degrees and keep it tucked gently against your side.
3. Hold a very light dumbbell or begin without weight.
4. Rotate the forearm upward while keeping the elbow still.
5. Lower slowly and with control.

This exercise targets external rotation and is commonly used in rotator cuff rehabilitation.

Resistance-Band External Rotation

1. Anchor a resistance band at elbow height.
2. Stand sideways to the anchor with the working arm farther from it.
3. Bend the elbow to 90 degrees and keep it near your ribs.
4. Pull the forearm outward against the band.
5. Return slowly to the starting position.

Avoid twisting your trunk or allowing the shoulder to shrug upward.

Prone Horizontal Abduction With External Rotation

1. Lie face down on a stable surface with one arm hanging toward the floor.
2. Turn the thumb upward.
3. Raise the arm out to the side in line with the shoulder, using a short and controlled range.
4. Keep the neck relaxed and do not force the shoulder upward.

This movement should be introduced gradually, particularly if you have shoulder pain or poor overhead tolerance.

Face Pulls

1. Set a cable or resistance band around face height.
2. Pull the handles toward your face while keeping your chest tall.
3. Finish with the upper arms in line with the shoulders and the shoulder blades gently drawn back.
4. Return slowly.

Face pulls can train the upper back, posterior shoulder, and scapular-control muscles alongside the rotator cuff.

Frequently Asked Questions

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