Interspinales Lumborum 1–4
Back · Trunk
The interspinales lumborum are short, paired muscles of the deep back that lie on either side of the interspinous ligament in the lumbar region. Each connects the superior surface of one lumbar spinous process to the inferior surface of the spinous process of the vertebra immediately above, bridging a single segment right at the midline. Working between adjacent spines, they extend the lumbar vertebral column and help stabilise neighbouring vertebrae. They are innervated by the posterior (dorsal) rami of the lumbar spinal nerves. Because they run purely vertically between spinous processes, they are well placed to provide extension and, importantly, proprioceptive feedback about segmental position.
Origin, Insertion, Action & Nerve
Origin
Superior surface of a lumbar spinous process
Insertion
Inferior surface of the spinous process of the vertebra above
Action
Extends the lumbar vertebral column and stabilizes adjacent vertebrae
Nerve
Posterior (dorsal) rami of lumbar spinal nerves
Attachments explained
The Interspinales Lumborum 1–4 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
Superior surface of a lumbar spinous process
Insertion
Inferior surface of the spinous process of the vertebra above
Action & function
When the Interspinales Lumborum 1–4 contracts, it produces the following movement: Extends the lumbar vertebral column 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 Interspinales Lumborum 1–4 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 Interspinales Lumborum 1–4, impairing the movements it normally produces (extends the lumbar vertebral column and stabilizes adjacent vertebrae). This is why knowing the innervation is central to localising nerve lesions in clinical practice.
How to study the Interspinales Lumborum 1–4 (the OIANS method)
Anchor interspinales lumborum by their name and geometry: inter-spinales means between the spinous processes, and each little muscle joins one lumbar spine to the next straight up the midline. That purely vertical, single-segment course makes extension their obvious action, since pulling adjacent spines together tips the segment backward.
Because they sit in the midline and span only one level, think of them, like the interspinales elsewhere, as extensors and position sensors rather than powerful movers. Study them as a paired series in the lumbar region running beside the interspinous ligaments, and pair them conceptually with the intertransversarii, which do the same short-segment job between transverse processes for lateral flexion and stability.
Frequently asked questions
Where is the Interspinales Lumborum 1–4 located?
The Interspinales Lumborum 1–4 is a muscle of the Back group, located in the Trunk.
What is the origin of the Interspinales Lumborum 1–4?
Superior surface of a lumbar spinous process
What is the insertion of the Interspinales Lumborum 1–4?
Inferior surface of the spinous process of the vertebra above
What movements does the Interspinales Lumborum 1–4 produce?
Extends the lumbar vertebral column and stabilizes adjacent vertebrae
What nerve supplies the Interspinales Lumborum 1–4?
Posterior (dorsal) rami of lumbar spinal nerves
Is the Interspinales Lumborum 1–4 free to study in OIANS?
The Interspinales Lumborum 1–4 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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