Anatomy Atlas

Subscapularis

Musculus subscapularis
MuscleHigh-yielddraftMSK

Large rotator cuff muscle on the costal surface of the scapula. It is the main medial rotator of the arm and the only cuff muscle inserting on the lesser tubercle.

Core anatomy

Location

Subscapular fossa, forming most of the posterior wall of the axilla.

Group

Rotator cuff (SITS); scapulohumeral muscles.

Origin

Subscapular fossa (costal/anterior surface) of the scapula.

Insertion

Lesser tubercle of the humerus.

Innervation

Upper and lower subscapular nerves from the posterior cord (C5, C6) verify

Blood supply

Subscapular artery and its branches verify

Action
  • Medially (internally) rotates and adducts the arm
  • With the other rotator cuff muscles, holds the humeral head in the glenoid cavity (anterior stabilizer)
Relations

The tendon passes anterior to the glenohumeral joint capsule, separated from the scapular neck by the subtendinous bursa of subscapularis, which usually communicates with the joint cavity. It forms part of the stabilizing sling for the long head of biceps brachii at the entrance of the intertubercular groove.

Forms a boundary of

Mentioned in

Generated automatically from links in other entries.

Rotator cuff (SITS)Lateral view of the right glenoid fossa with the humerus removed, anterior to the right. Supraspinatus passes over the top of the joint beneath the acromion, infraspinatus and teres minor lie behind it, and subscapularis lies in front. The long head of biceps arises from the supraglenoid tubercle and the long head of triceps from the infraglenoid tubercle. The inferior part of the capsule has no cuff support. The table lists each muscle: supraspinatus to the superior facet of the greater tubercle, suprascapular nerve, initiates abduction, empty-can test; infraspinatus to the middle facet, suprascapular nerve, lateral rotation; teres minor to the inferior facet, axillary nerve, lateral rotation; subscapularis to the lesser tubercle, upper and lower subscapular nerves, medial rotation, lift-off and belly-press tests. All are supplied mainly by C5–C6.SupraspinatusInfraspinatusTeres minorSubscapularisAcromionCoracoid processLong head of biceps(supraglenoid tubercle)Rotator intervalInferior capsule: no cuff(dislocation is usuallyanterior–inferior)Long head of triceps(infraglenoid tubercle)Glenoid fossaand labrumRight glenoid, lateral view, humerus removedposterior ← · → anterior · not to scaleMuscleHumerusNerveActionExam testSupraspinatusGreater tubercle (superior facet)SuprascapularInitiates abductionEmpty canInfraspinatusGreater tubercle (middle facet)SuprascapularLateral rotationResisted ERTeres minorGreater tubercle (inferior facet)AxillaryLateral rotationResisted ER, hornblowerSubscapularisLesser tubercleUpper + lower subscapularMedial rotationLift-off, belly pressAll four are supplied mainly by C5–C6. Supraspinatus initiates abduction (about the first 15°);deltoid takes over after that. Supraspinatus is the tendon most often torn or impinged under theacromion. Supraspinatus, infraspinatus and teres minor insert on the greater tubercle; subscapularis on the lesser.

Swipe sideways to see the whole diagram →

Rotator cuff (SITS). Right glenoid seen from the side with the humerus removed. The cuff covers the top, back and front of the joint but not its inferior part, which is why most dislocations are anterior–inferior. The table summarizes attachments, nerves, actions and bedside tests.
Original schematic, created for this atlas.
Pectoralis minor, serratus anterior, subscapularis in the posterior wall of the axilla, coracobrachialis, biceps brachii and brachialis
Subscapularis forming the posterior wall of the axilla.
Henry Vandyke Carter, Gray's Anatomy of the Human Body, 20th ed. (1918), Fig. 411. Source · Public domain (Public domain in the US: published before January 1, 1931 (per Wikimedia Commons))

Clinical correlations

Subscapularis tear

Mechanism / lesion

Forced external rotation or hyperextension, or anterior dislocation (especially in patients over ~40). Can also be degenerative.

Classic presentation

Anterior shoulder pain and weak internal rotation. Increased passive external rotation compared with the other side. Positive lift-off and belly-press tests. May be associated with medial subluxation/dislocation of the long head of biceps tendon.

High-yield PANCE pearls

  • Subscapularis = main internal rotator; inserts on the lesser tubercle.
  • Tests: lift-off (Gerber), belly-press, bear-hug.
  • Consider a subscapularis tear in an older patient with persistent weakness after an anterior dislocation.

Imaging anatomy

X-ray

Usually normal.

MRI

Axial images are best for the subscapularis tendon and lesser tuberosity insertion. Look for an empty or medially displaced biceps tendon from its groove when the subscapularis tendon is torn.

Ultrasound

Scanned anteriorly with the arm externally rotated. The tendon is seen in long axis inserting on the lesser tuberosity. Dynamic rotation can show medial subluxation of the biceps tendon.

Key views & landmarks
  • MRI axial proton density fat-sat through the lesser tuberosity

Physical exam

Surface landmarks

The muscle is largely inaccessible. The tendon insertion can be palpated at the lesser tubercle, medial to the intertubercular groove, with the arm externally rotated.

Strength / function testing

Resisted internal rotation with the elbow at the side.

Lift-off test (Gerber)

Technique

The patient places the dorsum of the hand on the lower back (lumbar region) and tries to lift the hand away from the back.

Positive test

Unable to lift the hand off the back, or does so only by extending the elbow or shoulder.

Significance

Subscapularis tear or dysfunction. Requires enough internal rotation to reach the position.

Belly-press test

Technique

The patient presses the palm against the abdomen with the wrist straight, bringing the elbow forward in front of the trunk.

Positive test

The elbow drops back behind the trunk, or the wrist flexes to generate pressure.

Significance

Subscapularis tear. Useful when the patient can't reach behind the back.

Self-quiz

Q1.

A 62-year-old man dislocated his shoulder anteriorly 6 weeks ago. He still has anterior shoulder pain. When he places the back of his hand against his lower back, he can't lift it away. Which tendon is most likely torn?

Show answer

D

A positive lift-off test indicates subscapularis weakness. Subscapularis is an anterior stabilizer and can tear with anterior dislocation, especially in older patients.

Q2.

Subscapularis inserts onto which structure?

Show answer

B

Subscapularis is the only rotator cuff muscle that inserts on the lesser tubercle. The other three insert on the greater tubercle.

Q3.

Which nerves supply subscapularis?

Show answer

B

The upper and lower subscapular nerves (posterior cord) supply subscapularis. The lower subscapular nerve also supplies teres major, and the thoracodorsal nerve supplies latissimus dorsi.

Q4.

Ultrasound of a patient with a complete subscapularis tear shows the long head of biceps tendon out of the intertubercular groove. In which direction is it usually displaced?

Show answer

A

The subscapularis tendon forms part of the sling that holds the biceps tendon at the entrance of the groove. When it tears, the long head of biceps can subluxate or dislocate medially.

Q5.

Which exam finding suggests a subscapularis tear?

Show answer

D

With subscapularis (the main internal rotator) torn, the shoulder shows increased passive external rotation, weak internal rotation, and positive lift-off and belly-press tests. Reduced passive external rotation suggests adhesive capsulitis.

Flashcards

See also