04 Feb New Research Explains Why Manipulation is Effective.
The following comments were triggered by a recent blog by Dr. Leon Chaitow. In it he sites some very interesting new research helping to explain what may be occurring during manipulation of spinal joints. Read his blog below: Does HVLA Manipulation Break Adhesions in Z Joints? By Leon Chaitow, D.O., N.D. A few things to clear up first. HVLA stands for high velocity low amplitude adjustment(manipulation) whereby the practitioner(usually a D.C. or D.O or DPT) applies a short, fast thrust into a joint for the purpose of seperatinng the joint surfaces and restoring normal motion and or positioning to a joint. Z joints stand for zygopohyseal joints in the spine and are depicted below. These are the joints that are typically manipulated during spinal manipulation. 
Pictures above(CT and cross section) are from Cramer & Darby Basic and Clinical Anatomy of the Spine, Spinal Cord, and ANS. Second edition. 2005 Of notable research showing that HVLA manipulation does in fact induce “gapping” of the Z joints are listed below and can be found on PubMed. In a recent Cochrane review for mechanical neck disorders, manipulation made it into the highest level of evidence. These studies below show exactly what is occurring in the Z joints during manipulation.
Evaluating the relationship among cavitation, zygapophyseal joint gapping, and spinal manipulation: an exploratory case series.
Cramer GD, Ross K, Pocius J, Cantu JA, Laptook E, Fergus M, Gregerson D, Selby S, Raju PK.