Multifidus lumborum muscle

At a glance

English

Multifidus lumborum muscle

Latin (TA2)

Musculus multifidus lumborum

System

Muscle

Region

Back

Side

Paired, left and right

About the multifidus lumborum muscle

Multifidus is a deep back muscle made of many short bundles, which is what its Latin name, split into many, describes. It belongs to the transversospinal group and runs the whole length of the spine from the sacrum to the axis. It is thickest in the lower back, where multifidus lumborum fills the hollow between the lumbar spines and the transverse processes, under the thoracolumbar fascia and medial to the erector spinae.

In this region its bundles spring from the mamillary processes of every lumbar vertebra, the small knobs on the back of each superior articular process. Lower bundles also come from the back of the sacrum, the posterior superior iliac spine and the deep surface of the erector spinae aponeurosis. Each bundle runs upward and inward to a spinous process two to four segments higher, with the deepest and shortest fibres crossing only one level and lying close to the facet joint capsules.

Its chief role is to stiffen and control each lumbar segment rather than to produce large movements. Acting on both sides it extends the lumbar spine and resists bending forward; acting on one side it helps to bend the spine to that side and to turn it slightly away. Its deep fibres switch on just before movement of the limbs, steadying the spine in advance.

Each segment of the muscle is supplied by the medial branch of a lumbar dorsal ramus, and blood comes from the dorsal branches of the lumbar arteries. In people with low back pain the lumbar multifidus often becomes smaller and partly replaced by fat on the painful side, and it may stay weak after the pain settles. Retraining it is a common aim of physiotherapy, and it is also stripped from the bone in posterior spinal surgery.

Attachments, action and supply

Origin

Mamillary processes of the lumbar vertebrae, back of the sacrum, posterior superior iliac spine and erector spinae aponeurosis.

Insertion

Spinous processes two to four segments higher.

Action

Steadies and extends the lumbar spine; on one side helps to bend it to that side and rotate it away.

Nerve supply

Medial branches of the dorsal rami of the lumbar spinal nerves.

Blood supply

Dorsal branches of the lumbar arteries.