Overview

The latissimus dorsi is a broad back muscle that narrows into a tendon at the front of the upper arm. It links the trunk to the shoulder and produces powerful pulling, climbing and swimming movements.

Location

Covers much of the lower and middle back
Forms part of the rear armpit fold
Passes around the teres major to attach to the humerus

Origin, Insertion, Nerve Supply, and Action

Origin: Lower thoracic spine, thoracolumbar fascia, iliac crest and lower ribs
Insertion: Floor of the intertubercular groove of the humerus
Nerve supply: Thoracodorsal nerve, C6–C8
Action: Extends, adducts and internally rotates the arm

Function

Powers pull-ups, rows and climbing
Drives the arm backward during swimming
Helps pull the body toward a fixed arm
Works closely with teres major

Structures It Connects To

Spine, pelvis and lower ribs
Humerus
Teres major
Thoracodorsal nerve

Movements It Assists

Shoulder extension
Adduction
Internal rotation
Pulling and pushing up from a chair

Common Injuries

Muscle or tendon strain
Tendon injury in throwing athletes
Load-related soreness after sudden increases in pulling volume

Pain Referral Patterns

Symptoms may be felt at the back of the armpit, side of the back or upper arm. Rotator-cuff and teres-major problems can feel similar.

Clinical Relevance

Latissimus injuries are uncommon compared with rotator-cuff problems but matter in swimmers, climbers and overhead athletes. Rehabilitation usually restores comfortable range before rebuilding pulling and high-speed force.

Interesting Facts

It is one of the widest muscles in the body.
Its tendon attaches beside teres major and pectoralis major, forming a compact arrangement around the bicipital groove.

References

StatPearls. "Anatomy, Back, Latissimus Dorsi." https://www.ncbi.nlm.nih.gov/books/NBK448120/
OpenStax. "Muscles of the Pectoral Girdle and Upper Limbs." https://openstax.org/books/anatomy-and-physiology-2e/pages/11-5-muscles-of-the-pectoral-girdle-and-upper-limbs
Schickendantz MS et al. Latissimus dorsi and teres major tears in professional baseball pitchers. https://pubmed.ncbi.nlm.nih.gov/19204367/

Latissimus Dorsi