The most common question new patients ask before their first adjustment is some version of: “Is it going to hurt?” The second most common is: “What’s that sound?” Both questions come from the same place — uncertainty about what’s actually happening when a chiropractor adjusts a joint.
The sound is a gas release, not a bone
The audible pop that often accompanies a chiropractic adjustment is called cavitation. Synovial joints — the facet joints of the spine, the sacroiliac joint, the shoulder, the knee — are enclosed capsules filled with synovial fluid and dissolved gases (mostly carbon dioxide and nitrogen). When the joint is moved rapidly through its end range, the pressure inside the joint capsule drops suddenly. The dissolved gases briefly form a gas bubble and collapse — that’s the sound.
The sound is incidental. An adjustment that doesn’t produce a sound is not an ineffective adjustment. The goal is not to produce the sound — it’s to restore normal motion to a restricted joint. The cavitation is simply a frequent byproduct of moving a joint through its paraphysiologic range.
What the adjustment is actually doing
A chiropractic adjustment is a high-velocity, low-amplitude (HVLA) thrust applied to a specific spinal segment. High velocity means it happens quickly — faster than the surrounding muscles can reflexively contract to resist it. Low amplitude means the joint moves a small distance — just enough to pass through its restricted end range and restore normal motion.
The mechanical effect is joint mobilization: restoring the normal arthrokinematic motion of the facet joint. But there is also a significant neurological effect. The rapid joint movement stimulates mechanoreceptors in the joint capsule and surrounding tissues, which inhibits nociceptive (pain) signaling through the gate control mechanism. This is one of the reasons patients often feel immediate relief after an adjustment — the neurological response is faster than the structural one.
Does it hurt?
In most cases, no. A properly delivered adjustment to a restricted segment typically produces a sensation of release — sometimes a brief moment of pressure, then relief. Patients who are acutely inflamed or highly guarded may feel more discomfort, which is why we always assess before adjusting and adapt technique to the presentation. There is no “one size fits all” adjustment. The force, speed, direction, and positioning are specific to you, your segment, and what your body is doing that day.
Written by Dr. Arthur Chakrian, DC — Spine Bar Chiropractic, Toluca Lake