Lumbar Rotator (Musculus rotator lumborum)

Anatomy

The deepest and most variable segment of the rotatores, situated in the lumbar gutter between the mammillary and spinous processes. Present in reduced form or intermingled with the multifidus, these short fascicles originate from lumbar mammillary processes and ascend to the spinous processes of the preceding vertebrae. They limit axial rotation in the lumbar spine—where facet orientation naturally prevents substantial twisting—and supply rich kinesthetic feedback.

Origin & insertion

From the mammillary processes of the lumbar vertebrae, into the base of the spinous process of the vertebra above.

Action

Weak contralateral rotator of the lumbar vertebrae; functions primarily to stabilize the intervertebral joints and prevent rotatory subluxation.

Innervation

Posterior rami of lumbar spinal nerves.

Clinical notes

Due to the sagittal orientation of lumbar facet joints, excessive twisting under axial compression tears the rotatores and facet capsular ligaments, causing acute lumbar sprain.

Related structures

• L2 — second lumbar vertebra
• L3 — third lumbar vertebra
• L4 — fourth lumbar vertebra

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