The iliocostalis muscles are a group of muscles along the lateral spine. They consist of the iliocostalis lumborum, iliocostalis thoracis and iliocostalis cervicis. These muscles are responsible for the erection, side bending and rotation of the spine. They also support posture and are involved in stabilizing the back. The iliocostalis muscles work together with other muscles of the back to maintain an upright posture and enable movement.