The rotatores muscle, also referred to as the rotatores spinae, is actually a cluster of 22 small muscles in the thoracic region. There are 11 rotatores muscles on each side of the spine. Each rotatores muscle is small and is classified as being quadrilateral in shape, meaning that each muscle has four sides.
The rotatores muscle, along with the multifidus and semispinalis muscles, facilitates the unilateral rotation (turning from side to side) and bilateral extension (bending backward and forward) of the spine. The three muscles comprise the transversospinalis muscle group and connect the transverse process (bony projection on the right and left side of each vertebra) to the superior spinous process (bony projections at the back of each vertebra) of the thoracic spine.
The transversospinales, erector spinae, and splenius muscles form the intrinsic back muscles, which are extensors of the spine. Extensors are muscles that help keep the back straight. It is essential to note that the intrinsic muscles of the spine serve to move the spinal column as well as to provide control of the spine.
Intrinsic muscles include superficial and deeper layers. The rotatores muscle belongs to the deeper layer intrinsic back muscles. They are, in fact, the deepest layer of muscles that cannot be felt through the skin.