A thin strip of tissue, the multifidus muscle starts at the sacral bone at the base of the spine and extends up to the axis, which is commonly referred to as the second cervical vertebra, or C2. The muscle features multiple insertion points along the spine, specifically into the spinous process of each vertebra. The spinous process is the bony projection at the back of each vertebra.
The posterior (rear) branches of the spine innervate the multifidus at various locations. The muscle features a lot of tendon-like fasciculi, or fiber clusters, that arise from the sacral, lumbar, thoracic, and cervical regions of the back. The multifidus muscle provides stiffness, stability, and support to the spinal column. It allows each vertebra to work more efficiently, and as a result, the muscle guards against spinal joint degeneration (or arthritis).