Erector Spinae

The erector spinae muscles are called the sacrospinalis in some older textbooks. They are also sometimes labelled extensor spinae.

The erector spinae muscles are a set of three overlapping groups of deep muscles. Together these muscle groups, which are situated along the spine, or 'vertebral column', of the human body, form the largest area of muscle on the posterior (back) of the human torso. The 3 groups of erector spinae muscles can be described as forming 3 approximately parallel vertical columns on each (right and left) side of the vertebral column - see diagram. In both cases the 'column' of erector spinae muscles closest to the mid-line of the body, i.e. the most 'medial' group of erector spinae muscles is the spinalis group, the next column of erector spinae muscles to the (right or left) side of the spinalis group is the longissimus group. The column of erector spinae muscles furthest from the (right or left) side of the vertebral column, i.e. the most 'lateral' group of erector spinae muscles is the iliocostalis group.

The 3 groups of erector spinae muscles and the individual* muscles comprising each group are:

• Spinalis (Group) - most medial
  • Spinalis capitis
  • Spinalis cervicis
  • Spinalis thoracis
• Longissimus (Group) - in between the spinalis and iliocostalis groups
  • Longissimus capitis
  • Longissimus cervicis
  • Longissimus thoracis
• Iliocostalis (Group) - most lateral
  • Iliocostalis cervicis
  • Iliocostalis thoracis (alt. Iliocostalis thoracic)
  • Iliocostalis lumborum (alt. Iliocostalis lumbar)

* The individual muscles listed as belonging to these groups varies slightly between textbooks and other resources. Not all lists include all the erector spinae muscles, some being larger and more powerful than others. Some older (historic) sources use different names for some or all of these muscles.

More about the names of the Erector Spinae muscles:

The 3 groups of erector spinae muscles that can be described in very simple terms as arranged in 3 columns (medial, intermediate and lateral) across the back, each include individual erector spinae muscles whose locations are identified approx. vertically, i.e. according to the section of the spine to which they are attached. The names of the individual erector spinae muscles are formed from the name of the group to which the individual muscle belongs and a word that refers to the location of the point(s) of insertion of that muscle. The words used to refer to the locations of the points of insertion of the individual erector spinae muscles are also descriptive and similar to other anatomical expressions used to refer to other structures at the same location in the body - see the following table, which also includes a short simple 'layman's terms' description of the approximate vertical location in the body.

As for all the other muscles described in this section, each of the individual erector spinae muscles has its own point(s) of origin, point(s) of insertion and action(s). Although advanced study of the muscles of the human body requires detailed knowledge of these muscles (including their structure, attachments incl. tendons, functions, typical uses, disorders and so on), many introductory courses treat the erector spinae muscles as an important group of deep muscles.

Actions of the 3 groups of Erector Spinae muscles:

Rather than listing and learning the actions of each of the individual erector spinae muscles, the actions of the muscles in each of the 3 groups can be considered together. Although less specific, this simplification amounts to a meaningful overall impression.

The approximate location of the erector spinae muscles (in general) is labelled on our diagram of human posterior muscles, which indicates that they are attached to multiple sites along the spinal column.