The radiate (stellate) ligament of the rib head is a fan-shaped ligament spreading from the anterior surface of the rib head to the intervertebral disc and the adjacent vertebral bodies above and below. It reinforces the anterior costovertebral joint capsule and provides the anterior stability to the rib head at its dual vertebral articulation. The interarticular ligament divides the costovertebral joint into superior and inferior compartments.
Prevents anterior displacement of the rib head from the costovertebral facets, maintains the dual rib-vertebral body articulation, and absorbs anterior costovertebral loading during rib rotation in respiration.
The radiate ligament is disrupted in rib head dislocation and in fracture-dislocations of the thoracic spine where the rib articulation is avulsed from the vertebral body. In diffuse idiopathic skeletal hyperostosis (DISH) and ankylosing spondylitis, ossification of the costovertebral radiate ligament produces a rigid thoracic cage with severely restricted respiratory excursion. The ligament is divided in costotransversectomy approaches, along with the costotransverse ligaments, to allow rib head removal for access to the anterior thoracic spine.
Enthesitis and progressive ossification of the radiate ligament at the costovertebral joints in ankylosing spondylitis produces the classic bamboo spine appearance with syndesmophytes bridging the disc spaces and fused costovertebral articulations, severely limiting thoracic expansion and chest wall compliance.
