The statistical distribution of members of a population around the population mean. In a gaussian distribution, 68.2% of values fall within Â± 1 standard deviation (SD); 95.4% fall within Â± 2 SD of the mean; and 99.7% fall within Â± 3 SD of the mean. Synonym(s): bell-shaped curve, normal distribution.
Located on the bony extensions of the vertebrae, the surfaces of the facet joints fit together like a three-dimensional puzzle. In the spaces between vertebrae run the nerve rootsâexits off the spinal cord's information highway.
Motion within the intervertebral complex occurs at the facet joints, vertebral bodies and the intervertebral disc. Hypertrophy of the facets occurs mostly in the lumbar and cervical regions, but rarely in the thoracic level. Studies show that the facets between L3-4, L4-5, and L5-S1 experience the greatest amount of stress with forward and lateral flexion. This predisposes those areas to experience an increased amount of repetitive strain and inflammation, which can lead to facet hypertrophy and other degenerative changes 3.