Spinal manipulation is a unique form of hands-on treatment (manual therapy) that is distinct from other forms of manual therapy such as massage and mobilization. While chiropractors sometimes refer to spinal manipulation as an "adjustment" or part of an adjustment, the term spinal manipulation is easier to define, more precise, and more widely used worldwide.
What is Spinal Manipulation?
Spinal manipulation is the application of a force (a quick, shallow thrust) to spinal joints that moves the target joint or nearby joints slightly beyond their normal range of movement. Spinal manipulation is often accompanied by an audible "pop." This is believed to be dissolved gas released from joint fluids by a quick drop in pressure. This gas suddenly joins into small bubbles, making a popping sound. Studies have shown that it is not always necessary to hear the audible pop for a spinal manipulation to be effective.
What is Palpation?
1) Static palpation – Palpation refers to the Doctor of Chiropractic using his or her hands to feel for normal motion. The joints of a spine should be able to rotate and translate through several axis of movement, and when they can't symptoms develop. These symptoms can include muscle tension or spasm, areas of hot or cold on the skin, or feeling the bones of the spine actually being out of alignment by running a hand down the spine and noting which bones do not line up with the bones above and below. Sometimes, the location needing adjustment is tender, or may refer pain, numbness or tingling to another part of the body when touched.
2) Motion palpation – this type of palpation involves movement, such as when the Doctor of Chiropractic uses his or her hands to rock he spinal bones back and forth to note if some are “stuck together” or simply not moving at all. When bones are stuck together the process of moving one bone will cause the other to move with it. Sometimes moving a vertebral bone will cause pain at the location of the bone, or will send pain, numbness or tingling, or shooting pain down an arm or leg or other part of the body.
What happens during a chiropractic adjustment?
When a chiropractor adjusts a spinal bone there are a number of things happening. I will describe the anatomical and biological processes involved in as simple a manner as possible without dumbing it down.
The importance of the set-up – In order to adjust a joint fixation the joint in question must first be brought to a point of tension. A proper and safe adjustment requires the spinal joint to be first maximally stretched so that the adjustment need only involve a minimal amount of force. This way, the joint is gently pushed beyond it’s limit with a final nudge.
Many times the person who needs an adjustment has tenderness in the area of the fixation, so the proper way to adjust it in order to minimize discomfort to the patient is to perform a proper set-up by bringing the joint to tension, and then to apply a gentle additional force to complete the adjustment. This method reduces pain and discomfort and makes the procedure much safer.
That popping noise
That noise is actually gases “escaping” the joint capsule. When the joint is taken beyond it’s normal range the capsule experiences brief negative pressure inside it which pulls nitrogen and other gases through the membrane, causing a popping noise in each joint adjusted. You can verify to yourself that this noise is not bones hitting each other by simply pulling your fingers and hearing them pop. Clearly, the bones are separating, not colliding.
Why it feel so good
While the adjustment does some obvious things like restore joint mobility in an area of fixation, it also causes some other things to happen as well. By relieving pressure on the nerve roots at the spine, the muscles those nerves feed will relax, and the pain from those injured nerves may disappear within a very short time.