The longissimus is the largest and most central column of the erector spinae, spanning the full length of the back and neck from the sacrum and iliac crest to the mastoid process. It is the primary extensor and postural stabiliser of the vertebral column, working continuously during all upright activities to counteract the forward gravitational force on the trunk. The thoracic portion is particularly important in spinal extension strength for lifting and carrying.
| Origin | Posterior sacrum, iliac crest, and spinous processes of L1 through L5 via the thoracolumbar fascia; Transverse processes of T1 through T4 or T5; Transverse processes of T1 through T5 and articular processes of C4 through C7 |
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| Insertion | Transverse processes of all thoracic vertebrae and 9 to 10 of the rib angles; Posterior tubercles of the transverse processes of C2 through C6; Posterior margin of the mastoid process |
| Nerve Supply | Posterior rami of spinal nerves at each level |
| Blood Supply | Posterior intercostal and lumbar arteries |
| Actions | Extension of the vertebral column and head when acting bilaterally; Ipsilateral lateral flexion and rotation of the vertebral column; Maintains erect posture of the trunk and head against gravity |
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The longissimus capitis, the uppermost portion, rotates the head ipsilaterally and works with the splenius capitis and oblique capitis muscles to control precise head positioning during visual tracking and balance tasks.
Longissimus trigger points are among the most common sources of referred low back and thoracic pain, producing aching across the back and into the buttock region. The thoracolumbar fascia, into which the longissimus inserts via its common tendon, plays a role in spinal load transfer and is thought to contribute to non-specific low back pain when its tension is abnormal. The longissimus is assessed during spinal extension strength testing and its endurance is measured with the Biering-Sorensen test.
The longissimus is palpable as the central band of the erector spinae mass, running 2 to 4 centimetres lateral to the spinous processes the full length of the back, becoming firm during resisted spinal extension or single-leg standing that requires lateral trunk stabilisation.
Acute muscle injury from sudden loading producing thoracic or lumbar pain with extension restriction, most common with combined flexion-rotation movements under load.
