Joints emit a variety of noises that people may describe as popping, cracking, clicking or catching. The technical term for these noises is “crepitus”, from the Latin term “to rattle”. People of all ages can experience crepitus, although it does become more common as we age.
So what causes crepitus?
Air bubbles forming in the joint spaces are the most common cause of popping noises. This noise occurs at joints where there is a layer of fluid within the joint space. When this happens, the low pressure in the joint space causes gases within the synovial fluid (a natural lubricant in the joint) to form a gas cavity, which comprises oxygen, nitrogen and carbon dioxide. Joints can be forced apart through natural everyday movements, or therapeutically, such as at the hands of a chiropractor.
Hearing these noises can be alarming, especially if you are not used to hearing your joints make this sound, however it is rarely a cause for concern.
Historically, there has been lots of debate about how this air bubble causes the popping noise.
The debate was not resolved until 2015 when a real time medical imaging study proved that it is the formation of the bubble that creates the noise. It then takes a while for the gases to re-accumulate – which is why you cannot immediately crack your knees or knuckles again.
Those with joint hypermobility (those that can move beyond the normal range of movement), often experience crepitus. This is because their joints can easily stretch further apart, allowing an air cavity to form. Joint hypermobility (which is different from the syndrome) is very common and affects 10-20% of people. Hypermobility is hereditary, which is why clicking joints may run in families.
You will probably have heard at some stage that if you crack your joints, you will get arthritis. Several studies have shown that this is not true, with one researcher cracking his own knuckles for 60 years, without changes in the joints.
Sometimes, there is an anatomical cause for the noise. This happens when tendons (tissue structures that connect muscles to bone) are moved over bony protrusions, and then quickly snap back into place. This noise is commonly heard in the knee when moving from a seated to a standing position, or when climbing the stairs as the tendons that cross the knee move over the joint. This increasingly occurs with ageing, as our muscles lose elasticity and decrease in size and strength. At the same time, changes occur in their tendons, which makes them stiffen.
The same thing can occur in the spine where hypermobility occurs due to an area of restriction. For example, with a prolonged sitting posture, the cervical spine can often be flexed for long periods leading to a subsequent decrease in neck strength. As a result, crepitus may occur as the surrounding musculature attempts to support the neck through regular movement.
When should you be concerned?
Joint spaces also contain layers of cartilage which assist with reducing the impact of the corresponding bones. Often in joint diseases such as Osteoarthritis, this cartilage has thinned and worn away, reducing the level of support between the bones. This thinning means the bones may come into direct contact and cause a sometimes painful, grinding sensation and associated noise. Worldwide, Osteoarthritis affects up to 50% of people over the age of 65, however 60% of all sufferers are of working age. The pain from osteoarthritis can be managed with various treatments.
Noisy joints are very common. Most of the time there is a physiological, rather than a pathological, cause for audible joints. If this is the case, the noises are nothing to worry about. But any noise coming frequently from the same joint and over a prolonged period, or causing pain, should be examined by your health professional. Get in contact with us if you would like more information.
Source: Edited from The conversation https://theconversation.com/what-makes-joints-pop-and-crack-and-is-it-a-sign-of-disease-113076