Iliocostalis

The iliocostalis is the lateral column of the erector spinae, a group of deep back muscles that run along the spine. It extends from the pelvis and lower spine to the upper thorax and neck, contributing to extension and lateral bending of the vertebral column and to postural control.

The iliocostalis has three parts: lumborum, thoracis, and cervicis. The three portions share the general role of upright posture and trunk movement, and they are organized in a continuous strip that spans the lumbar region to the ribs and cervical spine. The muscles are supplied by the dorsal rami of spinal nerves and receive blood from segmental arteries along the spine.

Iliocostalis lumborum originates from the posterior iliac crest, the thoracolumbar fascia, and the sacral region. It inserts mainly on the angles of the lower ribs (typically ribs 6–12) and, in some individuals, on the transverse processes of upper lumbar vertebrae (L1–L3). This portion primarily aids in extending and laterally flexing the lumbar spine.

Iliocostalis thoracis arises from the angles of the lower ribs (usually 6–12) and inserts on the angles of the upper ribs (approximately 1–6). It helps extend and stabilize the thoracic spine and contributes to rib movement during respiration.

Iliocostalis cervicis originates from the angles of the upper ribs (often ribs 3–7) and inserts into the transverse processes of the cervical vertebrae (C4–C6). It supports cervical extension and lateral bending, working with the other neck muscles to maintain posture.