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.
A facet joint has two bony surfaces with cartilage between them and a capsule of ligaments surrounding it. 1  Synovial fluid lubricates the joints, as is the case with other joints (e.g., the knee). 2  The primary cause of facet arthropathy is spinal degeneration which typically occurs in later life.