is always a less than ideal positioning of spinal segments. There is also always a reduced anterior to posterior dimension of the spinal canal compared to the way it is supposed to be. The greater the posterior displacement, the more significant it is for producing a dysfunctional spinal cord or even a cauda equina syndrome. Joint stability Joint stability is easily evaluated by the use of flexion and extension lateral x-ray views of the spine. A summary of part of the DRE tables (6) give a guide as to the implications of the joint instability. If either translation or angular change is determined from flexion to extension to the degree shown in the table below, then Category IV instability is present. See also Joint stability. Translation is a gliding motion where one bone of a joint glides over its neighbour. Management References 6. Hadley, Lee A. (MD), (1973) “Anatomicoroentgenographic Studies of the Spine”. 390. 7. Cocchiarella L., Andersson, G. “American Medical Association Guides to the Evaluation of Permanent Impairment”, 5th edition, Tables 15- 3, 15-4, 15-5. 8. Giles, L.G.F.; Muller R.; and Winter G.J. (2006) “Lumbosacral disc bulge or protrusion suggested by lateral lumbosacral plain x-ray film – preliminary results.” Journal of Bone and Joint Surgery. British Volume, Vol 88-B, Issue SUPP_III, 450. Deforming dorsopathies