Diffuse idiopathic skeletal hyperostosis (DISH) is not really an arthropathy because it spares synovium, articular cartilage, and articular osseous surfaces. It is a fairly common ossification process involving ligamentous and tendinous attachments to bones and occurs in 12% of the elderly (55). It most commonly affects the thoracic spine but also may involve the pelvis, foot, knee, and elbow. It can involve ossification of all the ligaments surrounding the vertebral bodies, particularly the anterior longitudinal ligament. Ossification of the posterior longitudinal ligament (OPLL) can also be seen. This is reported to be more common in orientals and can be responsible for significant spinal canal stenosis. By definition, DISH must involve a flowing ossification of at least four contiguous vertebral bodies (Fig. 6-43A,B). There must be normal disc spaces and facet joints, without joint sclerosis.