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Latissimus dorsi muscle

The latissimus dorsi is a large, flat, triangular muscle that forms the posterolateral wall of the trunk. It originates from the spinous processes of T7–T12 vertebrae, thoracolumbar fascia, iliac crest, and lower 3–4 ribs, with occasional slips from the inferior angle of the scapula. The fibers converge superolaterally to form a tendon that inserts into the floor of the intertubercular sulcus of the humerus.

The muscle is innervated by the thoracodorsal nerve (C6–C8) and supplied by the thoracodorsal artery, a branch of the subscapular artery. It functions as a powerful adductor, internal rotator, and extensor of the humerus, and plays an important role in climbing, swimming, and rowing movements.

Clinically, the latissimus dorsi is often used in reconstructive surgery as a myocutaneous flap, particularly in breast and chest wall reconstruction. Injuries and tears may occur in athletes, particularly in throwing sports and weightlifting.

Synonyms

  • Lats

  • Musculus latissimus dorsi

  • Broadest muscle of the back

Function

  • Adduction of the humerus (bringing the arm toward the body)

  • Internal rotation of the shoulder joint

  • Extension of the humerus from a flexed position

  • Assists in forced expiration by compressing the thoracic cage

  • Provides strength for climbing, swimming, and pulling activities

MRI Appearance

T1-weighted images:

  • Muscle appears as intermediate signal intensity with intramuscular fat streaks visible in older patients

  • Borders well defined by surrounding fat planes

T2-weighted images:

  • Normal muscle: intermediate to low signal

  • Edema, strain, or tears appear as hyperintense regions within the muscle fibers

STIR:

  • Suppresses fat, making muscle edema, strain, or inflammation clearly hyperintense

  • Useful in detecting acute injuries

T1 Post-Gadolinium (Gd-enhanced MRI):

  • Normal muscle shows mild uniform enhancement

  • Injured or inflamed areas show focal or diffuse increased enhancement

  • Helpful in detecting tumors, myositis, or vascularized flaps

MRI Non-Contrast 3D Imaging:

  • Provides volumetric reconstructions for pre-surgical planning of flaps

  • Defines muscle origin, insertion, and tendon continuity

CT Appearance

Non-contrast CT:

  • Muscle visualized as a soft tissue density along the posterior chest wall

  • Useful for detecting atrophy, fatty infiltration, or mass lesions

CT Post-Contrast:

  • Enhances muscle vascularity, highlighting injury, tumors, or infection

  • Provides detail of thoracodorsal vascular pedicle for flap planning

  • 3D reconstructions show relation to ribs, scapula, and humerus

CT images

Latissimus dorsi muscle anatomy CT axial image -img-00000-00000

CT images

Latissimus dorsi muscle anatomy ct coronal image -img-00000-00000

MRI images

Latissimus dorsi muscle anatomy MRI coronal image -img-00000-00000

MRI image

Latissimus dorsi muscle mri axial anatomy image-img-00000-00000