The multifidus is the primary segmental stabiliser of the lumbar spine, providing the deep intersegmental stiffness that the erector spinae cannot because of their long spans. In the lumbar region it is the largest and most important multifidus mass, and its selective atrophy on the painful side in acute low back pain — detectable by ultrasound or MRI within 24 hours of onset — is one of the most consistent findings in spinal pain research. Its atrophy does not spontaneously reverse even after pain resolution.
| Origin | Sacrum, mammillary processes of lumbar vertebrae, transverse processes of thoracic vertebrae, and articular processes of cervical vertebrae |
|---|---|
| Insertion | Spinous processes two to five levels above — the longest fibres span five levels, shorter fibres span two to three levels |
| Nerve Supply | Posterior rami of spinal nerves at each level |
| Blood Supply | Posterior intercostal and lumbar arteries |
| Actions | Extension and contralateral rotation of the spine; Segmental stabilisation of individual vertebral motion units; Controls intervertebral shear forces during movement |
|---|
The lumbar multifidus fires anticipatorily before limb movements to pre-stiffen the lumbar segment being loaded, along with the transversus abdominis — the deep local stabiliser system. This feedforward activation is specifically impaired in chronic low back pain patients, explaining the instability and recurrence that characterises the condition.
Multifidus rehabilitation using ultrasound biofeedback to visualise the muscle contracting during specific exercises is a cornerstone of chronic low back pain management. Real-time ultrasound shows the muscle thickening during voluntary contraction, providing immediate visual feedback. Lumbar multifidus atrophy correlates with the severity of disc degeneration and is an independent predictor of low back pain recurrence.
The lumbar multifidus is palpable with deep pressure immediately adjacent and lateral to the lumbar spinous processes, becoming firm during prone lumbar extension or during the specific multifidus activation exercise of gentle voluntary back tightening.
Selective multifidus atrophy and activation failure in acute and chronic low back pain producing segmental instability and predicting recurrence, managed with specific motor control retraining and ultrasound biofeedback.
