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Subscapularis muscle

The subscapularis muscle is a large triangular muscle located on the costal (anterior) surface of the scapula. It arises from the subscapular fossa and inserts onto the lesser tubercle of the humerus and the anterior part of the shoulder joint capsule.

It is the most powerful muscle of the rotator cuff group, functioning primarily as an internal rotator of the humerus. It also contributes to shoulder adduction and stabilization, keeping the humeral head properly seated in the glenoid cavity during arm movements.

The muscle is innervated by the upper and lower subscapular nerves (C5–C7), branches of the posterior cord of the brachial plexus, and receives its arterial supply from the subscapular artery (branch of axillary artery).

Clinically, the subscapularis is critical in rotator cuff pathology, anterior shoulder instability, tendon tears, and shoulder arthroplasty planning.

Synonyms

  • Subscapular muscle

  • Musculus subscapularis

Function

  • Primary internal rotator of the humerus

  • Assists with adduction of the arm

  • Stabilizes the humeral head in the glenoid cavity as part of the rotator cuff

  • Provides dynamic anterior shoulder stability

MRI Appearance

T1-weighted images:

  • Muscle belly: intermediate signal intensity

  • Tendon: low signal, best seen attaching to the lesser tubercle

T2-weighted images:

  • Normal tendon: uniformly low signal

  • Tears: focal hyperintense signal within tendon or discontinuity

  • Muscle edema appears hyperintense

STIR:

  • Excellent for detecting muscle edema, partial-thickness tears, or tendon inflammation

  • Suppresses fat for high contrast between tendon/muscle and pathology

T1 Post-Gadolinium (Gd-enhanced MRI):

  • Enhances in cases of tenosynovitis, muscle inflammation, or neoplasm

  • Post-op evaluation for repair integrity or scarring

MRI Non-Contrast 3D Imaging:

  • Provides multiplanar and 3D visualization of the tendon and its footprint

  • Useful for arthroplasty planning and surgical mapping

CT Appearance

Non-contrast CT:

  • Muscle appears as soft-tissue density; tendon as thin hypodense structure

  • Useful for calcific tendinopathy or bony changes at tendon insertion

CT Post-Contrast:

  • Enhances inflamed or vascularized soft tissues

  • Helps evaluate neoplasms, infections, or post-surgical changes

  • 3D reconstructions highlight bone-tendon relationships

MRI images

Subscapularis muscle mri AXIAL IMAGE

MRI images

Subscapularis muscle mri sag image

CT image

Subscapularis muscle anatomy ct coronal image -img-00000-00000

CT image

Subscapularis muscle ct axial