The main treatment method of chiropractors is the "chiropractic manipulative therapy" or commonly referred to as an "adjustment". In technical jargon, it is the act of "moving the joints of the spine beyond the individual's usual physiological range of motion using a fast, low amplitude thrust" [THE CHIROPRACTIC ACT, 1991]. This generates a release within the joint which may cause a sound as the movement takes place.
Doctor of Chiropractic perform adjustments to correct the misaligned or subluxated vertebrae and change the function of the joints of the body. Correcting dysfunction (subluxation) will have a beneficial effect on the nervous system and help in relieving pain and bringing you to optimum health. The adjustment is usually done by hand. It consists of placing the patient on a specially designed adjusting table and applying pressure, using specialized techniques, to the areas of the spine that are out of proper alignment or that do not move properly within their normal range of motion. During an adjustment the joint is moved past its passive range of motion but not past its anatomical limit. An audible "pop" is often associated with the procedure, which is the consequence of gasses being released within joint fluid. Since every patient is unique, each treatment and each adjustment is unique as well. Your age, size and individual spinal problems will determine which adjustment technique will best put you on the road recovery.
Making specific, corrective adjustments to the spine is not as new as you might think. Accounts of spinal manipulation appear in the writings of ancient Egypt, the Mayan and Incan cultures, and in the literature of Renaissance Europe where practitioners of manipulation were known as "bone setters".