They become less able to withstand forces placed upon them. If too much force is placed on them, they can be squeezed and expand or rupture. This rupture usually occurs in an upward direction, and the disk extrudes into the spinal canal where the spinal cord is. Signs develop either because of the force of the disk material hitting the cord, or due to the disk material compressing the spinal cord. Intervertebral disk disease can occur in any area of the spinal cord.
Dachshunds appear predisposed, as their disks age or degenerate quicker than most dogs.
Young to middle-aged dogs are most commonly affected. Dogs less than 1 year of age rarely have intervertebral disc disease. Geriatric dogs are occasionally affected. Clinical signs of disk disease are rare in cats. Signs of a disk problem range from being painful to being unable to move.