Chiropractic adjustment is a procedure in which trained specialists (chiropractors) use their hands or a small instrument to apply controlled, sudden force to a spinal joint. The goal of this procedure, also known as spinal manipulation, is to improve spinal motion and improve your body’s physical function.

As the joint is taken beyond its normal range of motion the 2 surfaces separate and then take approximately 20 minutes to return to their former position and pressure. The crack known as a cavitation is not from the bones but from the collapse of the gas bubble (80% CO2) formed by the low pressure in the joint fluid as the 2 surfaces separate. The phenomenon of joint fluid cavitation is central to the definition and effect of any manipulation. The negative pressure that normally helps to hold the cartilage together is temporarily decreased allowing more freedom and greater passive ROM. None of this occurs in mobilization.

Cavitation and increased range of motion causes an inhibition of pain. According to the Melzack and Wall gate mechanism the transmission of pain up the spinal cord can be increased by the lack of proprioceptive input (sensory information on the movements and positions of muscles) or reduced by greater proprioceptive input. Spinal facet joints are rich in mechanoreceptors. The nerve endings that give proprioceptive input through large nerve fibers which compete for central transmission with adjacent smaller pain fibers. Increased proprioceptive input from increased joint motion reduces or closes the gate on pain transmission.

Joint and muscle receptor stimulation causes relaxation of the paraspinal muscles. Wyke et al. has shown that stimulation of mechanoreceptors by stretching of the joint has a reflex effect on muscles over the joint, calming the muscle excitability and spasms that are often a part of lower back pain. Bernard and Cassidy state, after their research on sacro-iliac joints, that one could hypothesize that high velocity, short amplitude manipulation forcefully stretches hypertonic muscles against their muscle spindles leading to a barrage of afferent impulses/signals to the CNS. Therefore leading to readjustment of muscle tone and relaxation. It might therefore be possible that manipulation affects joints by stimulating Type I and Type II articulation mechanoreceptors as well as Type III in the overlying ligaments. These impulses travel along medium and large diameter nerve fibers and inhibit pain impulses travelling through small diameter fibers.

Breaking of joint adhesions is also an important mechanical effect. With chronic pain there is shortening of connective tissue, long-term reduced joint mobility and formation of adhesions. Adjustments result in increased motion and therefore decreased pain / pain inhibition by gate-control mechanism stated earlier. Release of trapped joint inclusions is another important effect of joint manipulation.

Lynton Giles (1980) demonstrated tags of fibrous cartilage and other tissues that become entrapped in lumbar and cervical facet joints. These may cause irritation and traction in both the affected and adjacent joints leading to reflex muscle spasm associated with acute locked back or neck (torticollis). Adjustments can release these joint tags. Stimulation of the Autonomic Nervous System (ANS) occurs during an adjustment. Korr et al. showed that spinal adjustments through cavitation and increased ROM can have reflex effects on the ANS which influences the vasomotor tone, in other words increase circulation in that area.

Chronic nerve irritation and compression can also by relieved by correction of abnormal joint mechanics. Kirkaldy-Willis and Cassidy have reported good results with many back pain patients with central and lateral canal stenosis. Giles has shown that while the entrance to the IVF is quite spacious for the exiting spinal nerve root, the neural and associated vascular structures within the “inter-pedicular zone” (where there is minimal extra space) may well be compromised by abnormal joint mechanics. Some patients will have a combination of stenosis and restricted joint motion. For many of them spinal adjustments will increase range of motion therefore relieving chronic intermittent nerve root compression and muscle dysfunction.

The following list is an attempt to describe the proposed effects of spinal adjustments.

• Increase in the active ROM via restoration of the normal axis of rotation (motion in all three planes)
• Reduction of pain
• Increase in skin pain tolerance level
• Increase in paraspinal muscle pressure pain tolerance
• Reduce muscle electrical activity and tension
• Consistent, reliable reflex responses in muscles in the spine and limbs
• Release entrapped meniscoid hyperplastic synovial tissue or synovial folds
• Breaking of contractile adhesions and collagen adhesions in the local soft tissue and supporting structures
• Effect upon the intervertebral disc either in the form of intradiscal block or generalised effects in the process of disc protrusion.
• Various anatomical responses including vasomotor changes, sudomotor activity (sweat gland activity) and changes in visceral regulation control. For example:
  • Blood flow and distal skin temperature changes
  • Blood pressure
  • Blood chemistry changes:
    • Increased secretion of melatonin
    • Increase plasma beta endorphin levels
    • Elevation of Substance P
    • Enhanced neutrophil burst
  • Control of pupillary diameter

Causes of fixation

Many mechanisms have been suggested as the cause of joint fixation. Fixation can be either intra-articular of extra-articular

1. Intra-articular

•  Derangement of the posterior joints
•  Intracapsular adhesions
•  Intradiscal derangement

2. Extra-articular

•  Segmental muscle spasm
•  Periarticular fibrosis and shortening
•  Adhesions

What you can expect

At your initial visit, your chiropractor will ask questions about your health history and perform a physical exam, with particular attention to your spine. Your chiropractor may also recommend other examinations or tests, such as X-rays. 

During the procedure

During a typical chiropractic adjustment, your chiropractor places you in specific positions to treat affected areas. Often, you’re positioned lying face down on a specially designed, padded chiropractic table. The chiropractor uses his or her hands to apply a controlled, sudden force to a joint, pushing it beyond its usual range of motion.

You may hear popping or cracking sounds as your chiropractor moves your joints during the treatment session.

After the procedure

Some people experience minor side effects for a few days after their first chiropractic adjustment. These may include headaches, fatigue or pain in the parts of the body that were treated.