A normal joint is stable and mobile within physiological limits. The stability is a result of the construction of the bones and cartilage, capsule, ligaments and muscles. Abnormalities in one or more of these elements can lead to instability of the joint; for example, an abnormal bone growth, rupture of ligaments or tendons and (sub)luxation by a traumatic incident. Instability leads to disproportionate mechanical loading of the joint and to degenerative changes such as cartilage erosion and osteoarthritis. The intervertebral disc strongly influences the stability of the spine.
From AVOM viewpoint degeneration of the intervertebral disc leads to spinal instability. This instability can cause misalignment of successive vertebrae and as a consequence of this misalignment and disc degeneration, herniation of the intervertebral disc results.