Chiropractic care is a hands-on, non-surgical approach focused on disorders of the musculoskeletal system, particularly the spine, and the nervous system that controls it. This form of care addresses mechanical issues that may affect the body’s overall function and health. The primary treatment method involves manual procedures to improve mobility and alignment.
The Foundational Concept of Spinal Dysfunction
Chiropractic intervention aims to correct a localized loss of normal movement within a spinal joint, often called functional spinal dysfunction. This dysfunction involves an alteration in the movement, alignment, or physiological function of a spinal segment, even if the joint surfaces are intact. Loss of proper movement can result from tissue injuries, acute trauma, or repetitive stresses like poor posture.
When a spinal joint loses its normal range of motion, surrounding tissues undergo changes that cause inflammation and pain. This dysfunction can irritate nearby neurological structures, including the spinal nerves exiting between the vertebrae. Restoring natural mobility and function to these restricted joints is necessary to alleviate tissue irritation and optimize neurological feedback.
Applying Spinal Manipulative Therapy
The specific procedure used to correct spinal dysfunction is Spinal Manipulative Therapy (SMT), commonly called an adjustment. This technique uses a high-velocity, low-amplitude (HVLA) thrust—a short, rapid force delivered to a specific, restricted joint. The force is applied precisely to move the joint past its normal physiological range of motion, but not beyond its anatomical limit.
This manual intervention restores mobility to the hypomobile, or restricted, joint. The audible “pop” or “crack” accompanying the HVLA thrust is known as a cavitation. This sound is caused by the sudden release of gas, primarily carbon dioxide, from the synovial fluid.
The noise is a byproduct of pressure change within the joint, not the therapeutic goal of the adjustment. The mechanical objective is to increase joint space and restore the joint’s ability to move freely. A faster thrust requires less total force to produce the therapeutic effect, making the force application rate clinically relevant.
Neurological and Physiological Changes
The effects of spinal manipulation extend beyond joint mechanics, initiating a cascade of neurological and physiological changes throughout the body. The HVLA thrust stimulates mechanoreceptors, which are sensory nerves located in the joint capsules and surrounding connective tissues. This stimulation sends a flood of non-pain signals to the central nervous system.
Pain Reduction
One immediate effect is pain reduction, partially explained by principles similar to the Gate Control Theory of Pain. The rapid input from the mechanoreceptors effectively “closes the gate,” overriding slower pain signals traveling to the brain. This mechanism allows the adjustment to provide immediate relief from spinal pain.
Proprioception and Motor Function
Manipulation significantly impacts proprioception, the body’s sense of its position and movement in space. Restoring normal joint motion allows mechanoreceptors to send more accurate feedback to the brain. This improved feedback can enhance balance, coordination, and overall motor function. Studies report that SMT can increase strength and improve balance in patients with certain conditions.
Muscle Tone
SMT also influences muscle tone in the affected area. Reducing the spinal joint restriction decreases the irritation that causes nearby muscles to become hypertonic or excessively tight. This reflexogenic response helps reduce muscle spasms and stiffness. It allows the musculature to relax and function more normally.
Autonomic Nervous System (ANS)
Beyond local effects, research suggests that spinal manipulation can influence the autonomic nervous system (ANS). The ANS controls involuntary bodily functions like heart rate and digestion. Some studies indicate that SMT may modulate ANS activity, sometimes increasing parasympathetic activity. This increase is associated with the body’s “rest and digest” state, suggesting spinal health can influence systemic function.