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Latissimus dorsi

Contents

Anatomy

Position

  • Superficial
  • Small portion deep to trapezius at lower insertion of trapezius thoracal area

Origin

  • Processus spinosi Th7-L5
  • Posterior sacrum
  • Crista iliaca posterior
  • Thoracolumbar fascia
  • 9-12th ribs
  • Angulus inferior scapula

Insertion

  • Medial lip of the intertubercular groove of humerus

Main function

  • Shoulder
    • Medial rotation
    • Adduction
    • Extension
  • Pelvis
    • Anterior tilt

Secondary function

  • Pelvis
    • Elevation
  • Scapula
    • Depression
  • Trunk
    • Lateral deviation
    • Elevation
    • Contralateral rotation

Segmental nerve innervation

  • Thoracodorsal nerve
  • C6-C8 (mainly C7)

Arterial supply

  • Thoracodorsal artery
  • Dorsal branches of posterior intercostal arteries

Referred pain pattern

Muscle type

  • Postural
    • Shortens when overactivated

Symptoms

  • Difficulties with movement of shoulder
  • Difficulties with overhead stretch

Body posture which can be affected

Due to it's ability to depress the shoulder to quite an extent it therefore can influence the position of the following body parts:

  • Shoulder
  • Neck
  • Pelvis
  • Trunk

Muscle attachment zones

Posterior view
Anterior view

Videos

Short version

Short version 2

Detailed version

Important functions

  • Together with the gluteus maximus the latissimus dorsi contributes significantly to the thoracolumbar fascia (Source 1) 
  • Latissimus dorsi may also have a role as an accessory breathing muscle and may affect both expiration or inspiration depending on the fixed position of the arm (Source 2)

Compensation

Muscles which compensates when this muscle is dysfunctional

Scaleni

  • It is plausible also to believe that when the plexus is pulled inferiorly, the scalene (possibly among others) will respond by tensing up and 'counter-straining' to avoid any more stretch which is enforced on it. Eventhough there is tension in the scalene, the solution is to resolve the tension in the latissismus dorsi as it is the cause for the tension in the scalene (hypothetical)

Increased tension in the muscle may cause problems with

Neck and shoulder pain

  • The latissimus dorsi pulls the shoulder girlde inferiorly which impacts the brachial plexus which might be compromised. This will further aggrevate neck and arms movements since the plexus is all ready pulled inferiorly

Myofascial lines

Superficial ventral arm line

Supportive dorsal line

Sources

  1. Vleeming A, Mooney V, Stoeckart R. Movement, stability & lumbopelvic pain: integration of research and therapy. Edinburgh: Churchill Livingstone, 2007.
  2. Dowling D. Evaluation of the thorax. London: Lippincott, 1991.