Anatomy Atlas

Teres minor

Musculus teres minor
MuscledraftMSK

Small rotator cuff muscle from the lateral border of the scapula. It laterally rotates the arm and is supplied by the axillary nerve.

Core anatomy

Location

Along the lateral border of the scapula, inferior to infraspinatus (often partly blended with it).

Group

Rotator cuff (SITS); scapulohumeral muscles.

Origin

Middle part of the lateral border of the scapula.

Insertion

Inferior facet of the greater tubercle of the humerus.

Innervation

Axillary nerve (C5, C6), via its posterior branch

Blood supply

Circumflex scapular and posterior circumflex humeral arteries verify

Action
  • Laterally (externally) rotates the arm
  • With the other rotator cuff muscles, holds the humeral head in the glenoid cavity
Relations

Forms the superior boundary of the quadrangular space (axillary nerve and posterior circumflex humeral artery). Together with teres major and the long head of triceps it also bounds the triangular space (circumflex scapular artery). It is the only rotator cuff muscle not supplied by the suprascapular or subscapular nerves.

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.
Posterior view of supraspinatus, infraspinatus, teres minor, teres major and triceps brachii
Posterior scapular muscles and triceps brachii.
Henry Vandyke Carter, Gray's Anatomy of the Human Body, 20th ed. (1918), Fig. 412. Source · Public domain (Public domain in the US: published before January 1, 1931 (per Wikimedia Commons))

Clinical correlations

Quadrilateral space syndrome

Mechanism / lesion

Compression of the axillary nerve in the quadrangular space, often in overhead athletes.

Classic presentation

Posterior shoulder pain and paresthesias. On MRI, isolated teres minor atrophy/denervation is a characteristic finding.

Axillary nerve injury PANCE

Mechanism / lesion

Surgical neck fracture of the humerus or anterior shoulder dislocation.

Classic presentation

Weak lateral rotation (teres minor) together with deltoid weakness and lateral shoulder numbness.

High-yield PANCE pearls

  • Teres minor is the only rotator cuff muscle innervated by the axillary nerve.
  • Superior border of the quadrangular space.
  • Hornblower's sign tests teres minor.

Imaging anatomy

X-ray

Not assessed directly.

MRI

Sagittal oblique images show muscle bulk. Isolated fatty atrophy or edema of teres minor suggests axillary nerve compression (quadrilateral space syndrome). Tendon tears are uncommon and usually part of a massive cuff tear.

Ultrasound

Seen from a posterior approach, inferior to infraspinatus, inserting on the lowest facet of the greater tuberosity.

Physical exam

Surface landmarks

Lies along the lateral border of the scapula. Difficult to separate from infraspinatus by palpation.

Strength / function testing

Resisted lateral rotation, especially with the arm abducted (teres minor contributes more in abduction).

Hornblower's sign

Technique

The arm is supported at 90° of abduction in the scapular plane with the elbow flexed at 90°. The patient tries to externally rotate against resistance (or bring the hand to the mouth).

Positive test

Unable to externally rotate in this position, or has to abduct the arm further (elbow rising like a horn player's).

Significance

Teres minor dysfunction, usually with a massive posterosuperior cuff tear.

Self-quiz

Q1.

Which rotator cuff muscle is innervated by the axillary nerve?

Show answer

C

Teres minor is supplied by the posterior branch of the axillary nerve. Supraspinatus and infraspinatus are supplied by the suprascapular nerve, subscapularis by the upper and lower subscapular nerves. Teres major is not part of the rotator cuff.

Q2.

Teres minor forms which boundary of the quadrangular space?

Show answer

A

Quadrangular space boundaries: teres minor (superior), teres major (inferior), long head of triceps (medial), surgical neck of the humerus (lateral).

Q3.

MRI of a 24-year-old baseball pitcher with posterior shoulder pain shows fatty atrophy limited to teres minor. Which structure is most likely compressed?

Show answer

B

Isolated teres minor denervation points to the axillary nerve in the quadrangular space (quadrilateral space syndrome). Deltoid may be involved too.

Flashcards

See also