The lumbar multifidus is the most important lumbar stabiliser, providing segmental control of each vertebral motion segment. It is the first muscle to atrophy following an acute disc herniation and the last to recover after back injury — its cross-sectional area reduction on MRI (measured at L4-L5) correlates with persistent LBP and recurrence risk. Specific multifidus activation exercises (low-load stabilisation) are the foundation of spinal rehabilitation.
| Origin | Mammillary processes of lumbar vertebrae and posterior sacral surface |
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| Insertion | Spinous processes of the vertebra 2-4 levels above — each fascicle spans multiple segments |
| Nerve Supply | Medial branch of the dorsal rami at each lumbar level |
| Blood Supply | Lumbar arteries |
| Actions | Extension and contralateral rotation of the lumbar spine; Segmental spinal stabilisation — the most important dynamic stabiliser of the lumbar motion segment; Reduces lumbar disc nuclear pressure during functional tasks |
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The multifidus has a high proportion of type I slow-twitch fibres suited to sustained low-load postural stabilisation. Its deep, short fascicles spanning 2-4 segments provide the fine-tuned control of intervertebral motion that global muscles (erector spinae) cannot provide.
Fatty infiltration and atrophy of the multifidus at L4-L5 and L5-S1 on MRI is associated with chronic LBP, disc pathology, and spondylolisthesis. Specific stabilisation exercises using ultrasound biofeedback to activate the multifidus independently of the erector spinae are the evidence-based approach to restoring multifidus function. After single-level TLIF, multifidus damage from retraction produces the paraspinal muscle atrophy seen on post-operative MRI.
The lumbar multifidus is palpable in the groove medial to the erector spinae, lateral to the spinous processes at each lumbar level, becoming firm during independent multifidus activation exercises.
Segmental multifidus wasting after acute disc herniation producing persistent lumbar instability managed with specific low-load stabilisation exercise targeting multifidus re-education.
