sidebending

Sidebending, or lateral flexion, is the movement of a body segment sideways away from the midline. In human anatomy, the term most often describes the lateral movement of the spine and head. For the spine, side bending occurs in the cervical, thoracic, and lumbar regions and is typically assessed together with flexion, extension, and rotation as part of spinal range of motion.

Mechanics and muscles: When the spine side-bends to one side, the vertebrae tilt and rotate within the constraints of the facet joints and supporting ligaments. The movement is produced by a combination of muscle groups on the contracting and lengthening sides. Primary contributors in the trunk include the ipsilateral erector spinae and quadratus lumborum, with supporting roles from the obliques, intercostals, and other paraspinal muscles. The abdominal wall and thoracolumbar fascia also influence the limit and quality of motion.

Range of motion: Normative values vary by region and age. Cervical lateral flexion is typically about 40–45 degrees, thoracic lateral flexion around 20–40 degrees, and lumbar lateral flexion roughly 20–30 degrees. In many movements, side bending is accompanied by some degree of rotation, especially in the thoracic region, whereas pure lateral bending is more limited by facet joints and ligaments.

Clinical relevance: Side bending is used in clinical examinations to assess spinal mobility, asymmetry, and pain sources. Abnormal side-bending ranges can indicate conditions such as scoliosis, degenerative changes, or muscular injury. Therapeutic approaches often incorporate side-bending exercises to improve flexibility, posture, and balance.