Rotatores Lumborum
Back · Trunk
The rotatores lumborum are the lumbar members of the rotatores, the deepest layer of the transversospinales, and are less distinct than their thoracic counterparts. Each arises from the mammillary process of a lumbar vertebra and passes upward and medially to attach to the base of the spinous process of the vertebra immediately above. Because they span only a short distance between neighbouring vertebrae, they rotate the lumbar spine toward the opposite side and act mainly as segmental stabilisers with a strong proprioceptive role. They are supplied by the posterior (dorsal) rami of the lumbar spinal nerves. As with all rotatores, their small size means they contribute far more to fine control than to gross rotation.
Origin, Insertion, Action & Nerve
Origin
Mammillary process of a lumbar vertebra
Insertion
Base of the spinous process of the vertebra above
Action
Rotates the lumbar spine to the opposite side and stabilizes adjacent vertebrae
Nerve
Posterior (dorsal) rami of lumbar spinal nerves
Attachments explained
The Rotatores Lumborum is defined first by where it attaches. Its origin is the more fixed anchor, usually the proximal or more stable end that stays put during contraction, while its insertion is the more mobile point that is pulled toward the origin when the muscle shortens.
Origin
Mammillary process of a lumbar vertebra
Insertion
Base of the spinous process of the vertebra above
Action & function
When the Rotatores Lumborum contracts, it produces the following movement: Rotates the lumbar spine to the opposite side and stabilizes adjacent vertebrae.
As part of the Back group of the Trunk, it works alongside neighbouring muscles to generate smooth, coordinated movement and to stabilise the structures it acts on.
Nerve supply & clinical relevance
The Rotatores Lumborum receives its nerve supply from the Posterior (dorsal) rami of lumbar spinal nerves.
Because a muscle can only contract when its nerve is intact, injury to the Posterior can weaken or paralyse the Rotatores Lumborum, impairing the movements it normally produces (rotates the lumbar spine to the opposite side and stabilizes adjacent vertebrae). This is why knowing the innervation is central to localising nerve lesions in clinical practice.
How to study the Rotatores Lumborum (the OIANS method)
Note the lumbar origin detail: because lumbar vertebrae lack prominent transverse processes to grip, the rotatores lumborum arise from the mammillary processes and run to the spinous process just above. That short span across one segment gives weak opposite-side rotation and, more importantly, tight segmental stabilisation of the lumbar spine.
Understand that the rotatores are inconstant and poorly defined in the lumbar region compared with the thorax, so study them as the deep lumbar echo of the clearer thoracic rotatores. Group them mentally with lumbar multifidus and intertransversarii as the deep proprioceptive and stabilising muscles of the low back, all supplied by lumbar dorsal rami.
Frequently asked questions
Where is the Rotatores Lumborum located?
The Rotatores Lumborum is a muscle of the Back group, located in the Trunk.
What is the origin of the Rotatores Lumborum?
Mammillary process of a lumbar vertebra
What is the insertion of the Rotatores Lumborum?
Base of the spinous process of the vertebra above
What movements does the Rotatores Lumborum produce?
Rotates the lumbar spine to the opposite side and stabilizes adjacent vertebrae
What nerve supplies the Rotatores Lumborum?
Posterior (dorsal) rami of lumbar spinal nerves
Is the Rotatores Lumborum free to study in OIANS?
The Rotatores Lumborum is always free to browse. Its full origin, insertion, action and nerve details are open to everyone in the Muscle Directory. Quiz and Flashcard practice for the Trunk is part of the one-time Lifetime upgrade, though; only the Upper Limb decks are free to test yourself on.
Related muscles
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