Crepitus is the name for the sounds that are audible under the skin and are made by the joints and tissues of the body. The sounds occur when two rough surfaces in the body collide or grind against each other. This can happen in conditions where the cartilage has worn away leaving the joints themselves to rub against each other; it can also occur where fractured bones scrape across each other. Cracking and popping in the neck may be painless or could be connected to arthritis and neck pain.
In addition soft tissue crepitus can occur when gas is abnormally present in an area, such as lung tissue in certain respiratory diseases, and also as gas gangrene in tissues infected with clostridium perfringens strains of bacteria. Subcutaneous crepitus occurs when air is trapped in the subcutaneous tissues, such as in surgical emphysema.
Many people crack their knuckles simply through habit, and produce a sharp cracking or popping sound, but many other joints can crack or be cracked when forced, such as the back, neck, hips, ankles, jaw, wrists, and even the toes.
A Palliative Action?
For those clicking or cracking their joints after exercise this can be a palliative action, with their muscles unable to stretch the joint into this position themselves. Examples include finger extension, distraction, flexion, and torsion; bending the finger away from the palm backwards, away from the hand, toward the palm, or twisting the fingers respectively. If the cause of the popping sound is due to cavitation then this can help relieve pressure in the joints and provide some relief from neck pain and other joint pain, although this is likely to just be temporary.
What Causes Neck Cracking Sound?
The joints are contained within a capsule that has fluid-producing synovial membranes in it. Cavitation is considered the most likely cause of most cracking and popping sounds and is due to the synovial fluid containing oxygen, nitrogen, and carbon dioxide, all of which can effervesce out of the fluid to form air bubbles. Spinal manipulation through chiropractic or osteopathic treatment can cause cavitation as the application of force leads to a change in pressure in the joint cavity, causing effervescence of gases and rapid air bubble collapse and the popping sound. An experienced and sensitive chiropractor will explain the, sometimes strange, noises that you hear during a spinal adjustment and, for the most part, these are not a cause for concern. Where a sharp crack and resulting neck pain occurs this clearly warrants reassessment and, although rare, arterial dissection may occur leading to strokes after chiropractic adjustment (see below).
Simple friction between joints can cause the popping sound, particularly in areas where cartilage deterioration has occurred. Another cause can be the stretching of tendons out of their usual place resulting in a popping sound when they return to their normal position. A mild dislocation when the bone or joint is stretched out of place is known as a subluxation, and a popping sound can occur when it snaps back into place; patients with temporomandibular joint syndrome can also cause the neck to crack. Au (1993) found that the joint popping associated with temporomandibular joint function was successfully treated in 18/22 young adults with the symptom by using isokinetic exercises, thus demonstrating that they were predominantly neuromuscular in origin.
Is Cracking Your Neck Harmful or Damaging?
There is a commonly held belief that cracking the knuckles or other joints can lead to arthritis although there is little evidence to support this idea (Swezey, 1975). Those who frequently crack their knuckles were, however, found in one study to have an increased incidence of hand-swelling and diminished strength of grip (Castellanos, 1990).
Other considerations apply, however, to cracking the neck. If acute neck pain is experienced when cracking the joints then it is advisable to consult a physician as it may indicate a degenerative joint condition. Obtaining relief from chronic neck pain by cracking the neck joints also necessitates medical attention as there may be better ways to correct the pathology causing the joint tension in the first place.
An Increased Risk of Stroke and Other Safety Concerns
There is some evidence that cracking the neck can increase the risk of stroke or other neurovascular events occurring. This evidence comes from the study of effects of chiropractic treatment and the deliberate spinal manipulation and neck cracking that can occur in this practice. A 2001 review of five studies by Ernst found a direct link between chiropractic treatment and mild-to-moderate, transient adverse effects experienced by nearly half of all patients. The most common complaints were local or radiating pain, neck pain headaches, and tiredness.
A further review by Ernst, in 2007, reported numerous severe complications and even deaths attributable to chiropractic treatment. These incidents often involved dissection of the vertebral artery or arteries, and on occasion dissection of the carotic artery, epidural hematoma, and pontine infarct (Parwar, 2001, Nadgir, 2003, Yokota, 2003, Saxler, 2004, ). In the majority of cases there is little information on the outcome of the patient, although dissection of the arteries and hematomas did result in infarctions (strokes) in some patients (Sedat, 2002, Jay, 2003).
Hypermobility and Chronic Neck Problems
It is suggested by some physicians that chronic cracking of the neck can cause a lack of elasticity in the neck muscles, allowing them to become fatigued more rapidly than usual and eventually lead to chronic neck pain from hypermobility. Hypermobility is where the joints are continually forced outside the usual realm of motion and, over time, this prevents them from returning to normal with repercussions in terms of being able to support the head without pain. It is very unlikely for the neck to become hypermobile, with this being more usually a condition of other joints in the body.
It is possible to feed the synovial fluid in the joints and ameliorate or slow down degeneration of the connective joint capsule. Supplements such as hyaluronic acid, glucosamine, chondroitin, MSM, and collagen may be beneficial.
Alternative therapies, such as yoga and pilates may aid in lengthening and relaxing the joints in the neck so as to reduce the likelihood of popping and cracking sounds. Exercises to strengthen the neck and back muscles may also help, but care should be taken not to overdevelop these muscles as this may lead to further tension, acute muscle fatigue, and spasm.
In conclusion, gentle cracking of the neck is unlikely to cause damage in the majority of cases, but in some circumstances can lead to an increased risk of stroke, hypermobility, or acute connective tissue or joint damage. Frequent desire to crack the neck may indicate an underlying joint condition causing tension in the neck muscles necessitating medical advice.