interspinous ligament interspinous ligament the interspinous ligaments (interspinal ligaments) are thin and membranous ligaments that connect adjoining spinous processes of the vertebra in the spine. interspinous ligamentmedian sagittal section of two lumbar vertebrae and their ligaments (interspinous ligament visible at center right)detailsfromspinous process of vertebratospinous process of vertebraidentifierslatinligamenta interspinaliata98a03.2.01.002ta21674fma71392anatomical terminology they extend from the root to the apex of each spinous process. they meet the ligamenta flava in front, and blend with the supraspinous ligament behind at the apexes of the spinal processes. the function of the interspinous ligaments is to limit ventral flexion of the spine and sliding movement of the vertebrae. the ligaments are narrow and elongated in the thoracic region. they are broader, thicker, and quadrilateral in form in the lumbar region. they are only slightly developed in the neck; in the neck, they are often considered part of the nuchal ligament.