Back Pain: Presence of pain on the posterior aspect of the body from the lower margin of the twelfth ribs to the lower gluteal folds; intensity of 4 or more on a 0–10 pain scale

Instability: Although the term instability is in common use and is felt to be important by some, no commonly agreed definition of the concept could be found by the expert panel. This should therefore be assessed by the examining physician, who should document his/her criteria used to determine the presence of instability, for example facet joint effusion, movement on flexion / extension sagittal x-ray, movement between standing and lying MRI or x-ray, subjective patient description as unstable, pain on initial movement after periods of inactivity/rest, Gower’s sign, segment angulation >10°, lateral olisthesis, traction spurs, ...