Baastrup's sign, or kissing spine, is an orthopedic and radiographic disorder that often occurs in elderly humans. It is characterized by enlargement of the posterior spinous projections of the lumbar spine, with normal intervertebral disc height and neuroforamina. The reason it is referred to as kissing spine is because the posterior spinous processes 'kiss' and touch one another as the individual goes into lumbar extension, for example when flat on their stomach. The condition has been seen in humans, canines, particularly with boxer breeds, and certain breeds of horses. This disorder is named after Christian Ingerslev Baastrup.

the appearance on a lateral view of the foot of an abnormal bony fusion of the calcaneus and navicular bones accompanied by a bony bar (tarsal coalition) extending between the two bones, with an elongated tubule-like extension of the anterior and superior process of calcaneus, fancifully likened to an anteater’s elongated nose.