The most common spinal surgery performed in the dog is for intervertebral disc disease. Intervertebral disc disease is the most common spinal disease in dogs and is increasingly recognised in cats. The intervertebral discs (IVD) are fibrocartilaginous cushions between the vertebrae (except the first 2 cervical vertebrae) that allow movement, are supportive and act as shock absorbers. They consist of a fibrous outer rim, the anulus fibrosis, and a jelly like centre, the nucleus pulposus. IVD degeneration results in diminished shock-absorbing capacity, and can ultimately lead to IVD herniation and spinal cord compression. The types of IVD herniation are often described as Hansen type I (nucleus pulposus degeneration and extrusion) and Hansen type II (anulus fibrosis degeneration and protrusion).