The Multifidus Muscle consists of a group of muscles located on either side of the spine, extending from the sacrum to the cervical spine. This muscle, which plays a critical role in stabilizing the spine, is a member of the transversospinalis muscle. Although anatomically superficial, it plays a functional role in enhancing spinal joint stabilization and mitigating interfacial friction during dynamic movements.

Anatomy

Morphology and Connection Points

The Multifidus Muscle is a deep back muscle located in the neck, back, and lumbar regions of the spine, providing segmental stability. The muscle originates from various points at different spinal levels. In the sacral region, it originates from the posterior surface of the sacrum, the sacrospinal ligament, and the posterior superior iliac spine. In the lumbar region, it originates from the mammary processes of the lumbar vertebrae; in the thoracic region, it originates from the transverse processes of the thoracic vertebrae; and in the cervical region, it originates from the articular processes of the lower four cervical vertebrae. The muscle fibers extend upward and medially, inserting onto the spinous processes of the higher vertebrae. Fiber length varies: the most superficial fibers reach 3–4 vertebrae superiorly, while the intermediate fibers extend 2–3 vertebrae superiorly. The deepest fibers directly connect adjacent vertebrae. This layered structure contributes to both segmental and overall spinal stability.

Embryological Origin and Classification

The Multifidus is a group of deep back muscles that develop from the epaxial (back) muscle mass. Embryologically, it originates from the dorsal region of somites derived from paraxial mesoderm. Located in the deep layer of the spinal musculature, the multifidus is classified within the transversospinal muscle group. This group also includes the semispinalis and rotatores muscles.

Nerve Innervation and Vascular Supply

The Multifidus Muscle is innervated by the posterior (dorsal) rami at the appropriate spinal levels. These nerves provide segmental control by giving direct branches to the muscle fibers at each vertebral level. Vascularly, the muscle is supplied by branches of the corresponding segmental arteries. Perfusion through these vessels meets the muscle's metabolic needs.

Function and Clinical Relationships

The Multifidus is one of the most important segmental stabilizer muscles of the spine. It lies deeper than the spinal erector group, transversus abdominis, and oblique muscles. This allows it to balance the load on the spine by limiting excessive movement of the spinal joints and improving mechanical efficiency. This deep location of the muscle plays a significant role in functional stabilization and regulating proprioceptive sensations. The lumbar multifidus, in particular, plays a key role in maintaining segmental control in the lumbar spine. Its activity is closely associated with the frequent occurrence of chronic low back pain. In the presence of pain, multifidus activity decreases due to reflex inhibition, and this atrophy process can persist even after the pain subsides. This can lead to spinal instability and a recurring pain cycle. Magnetic resonance imaging (MRI) and ultrasonography can be used to assess fatty infiltration and atrophy in the multifidus muscle. These imaging techniques are also useful for monitoring muscle quality and monitoring rehabilitation. During rehabilitation, activating the pelvic floor muscles—for example, consciously stopping the flow of urine—can help reflexively activate the multifidus. Furthermore, targeted exercises can reactivate the muscle and help prevent recurrence of low back pain.