Biomechanical definitions of spinal instability.
Instability is a mechanical entity, and an unstable structure is one that is not in a optimal state of equilibrium. In the spine, stability is affected by restraining structures that, if damaged or lax, will lend to altered equilibrium and thus instability. Instability is defined as loss of stiffness.
D001696:Biomechanical Phenomena; D006801:Humans; D007593:Joint Instability / Q000503:physiopathology*; D008159:Lumbar Vertebrae / Q000503:physiopathology*