Multifidus
Musculus multifidus
Also known as: transversospinalis, lumbar multifidus, rotatores, semispinalis
The middle layer of the transversospinalis group. Its short fascicles span 2–4 vertebrae, and it is thickest in the lumbar region, where it is a key segmental stabiliser of the spine.
Overview
The transversospinalis muscles run obliquely from transverse processes (or equivalent points) to the spinous processes above them, in three layers. Semispinalis is superficial and spans 4–6 segments. Multifidus is the middle layer and spans 2–4 segments. Rotatores are deepest and span 1–2 segments. Multifidus extends from the sacrum to C2. In the lumbar spine it is the largest and most medial muscle, filling the space beside the spinous processes, and it arises from the sacrum, the posterior superior iliac spine, the erector spinae aponeurosis and the mammillary processes.
Because its fascicles are short and segmental and are rich in muscle spindles, multifidus stiffens and controls each spinal segment rather than producing large movements. It also extends the spine and assists rotation to the opposite side. It is supplied segmentally by medial branches of the dorsal rami.
Anatomy
- Origin
Posterior sacrum, posterior superior iliac spine, erector spinae aponeurosis, mammillary processes of the lumbar vertebrae, transverse processes of T1–T12 and articular processes of C4–C7.
- Insertion
Spinous processes of vertebrae 2–4 segments above the origin (up to C2).
- Action
Stabilises the vertebral segments; extends the spine; rotates it to the opposite side (unilaterally).
- Innervation
Medial branches of the dorsal rami of the spinal nerves.
- Nerve roots
Dorsal rami C3–S3 (segmental)
- Arterial supply
Dorsal branches of the posterior intercostal, lumbar and lateral sacral arteries.
Function
- Stabilises individual vertebral segments (segmental stiffness)
- Extends the spine; assists rotation to the opposite side
- Proprioception of spinal position
Clinical significance
Multifidus in chronic low back pain
Ipsilateral atrophy and fatty infiltration of lumbar multifidus at the painful level occur rapidly after an episode of back pain and do not recover on their own. Specific motor-control rehabilitation targets this muscle.
Compiled from standard anatomy and physiology references — see the Muscular System sources. For education only; not medical advice.