Some noises made by your joints are harmless, but not all; here’s how to tune in and know the difference.

Most of us at one time or another will find ourselves bending or flexing our fingers and toes until we hear that satisfying “pop”. In fact, just about any joint is capable of producing a “pop” or “crack” at just about any time of the day. But, could this constant cracking and popping be doing damage to the joints?

The “popping” sound that we hear is actually not anything to worry about.  Greg Kwachuk, Professor of Rehabilitation Medicine at the University of Alberta in Edmonton, United States, took MRI videos of a chiropractor’s 10 fingers as they were pulled one by one until they popped.

They videos showed that the popping sounds were caused by gases dissolved in the fluid cushion between joints, known as the synovial fluid.  When we stretch the joints, the space between the bones increases, creating a vacuum, a process known as cavitation.  Because the fluid is not able to fill the space in time, the dissolved gases are drawn into the space and form a bubble that rapidly grows and then bursts, causing the popping noise.  When the bubble bursts, the gases simply dissolve back into the synovial fluid.  The dissolving process is also usually quite slow, during a time known as the refractory period, which is why people can normally only “pop” their joints every twenty minutes or so.

The bottom line, though, is that knuckle-cracking won’t give you arthritis.  In fact, there isn’t actually any evidence yet that can conclusively link arthritis to joint “popping”. In 1998, Dr Donald L. Unger sent a letter to the publication, Arthritis & Rheumatism which was published by the American College of Rheumatology detailing a study on himself over 50 years to determine whether joint cracking would lead to arthritis. For every day of those 50 years he cracked the joints on the left hand but not the right. Nothing happened.

However, that doesn’t mean all joint noises are completely harmless.  There is evidence to suggest that certain types of joint conditions could lead to increased frequency of “popping” and swelling after joints have been “popped” or other joint noises.  Loose ligaments, a condition known as ligamentous laxity, can contribute to more frequent joint cavitation because of the looseness of the ligaments that stabilise the joint.  More severe cases of the condition, or other conditions including joint hypermobility syndrome or Ehlers-Danlos syndrome, can lead to joint instability that results in injuries.  So, while the “popping” of joints on its own may not have any known medical complications, it still may be symptomatic of other conditions.

Joint Hypermobility Syndrome

Joint Hypermobility Syndrome (JHS) is a medical condition in which a person’s joints have an unusually large range of motion.  This is often called “loose joints” or “double-jointedness”.  It’s thought to be caused by genetically determined changes in the collagen in a person’s body and the condition is often hereditary.  As the collagen is weaker than it typically should be, tissues in the person’s body are often weaker too.  In particular, ligaments and other connective tissue.  This causes them to be loose and stretchy, often leading to joint instability.

The syndrome is often hard to diagnose simply because it has a very wide range of symptoms and effects.  Patients may have very mild cases that are barely noticeable, for example, fingers bending slightly further back than normal.  While others may experience more serious symptoms such stiffening and soreness in the joints, fatigue and even digestive problems such as Irritable Bowel Syndrome (IBS).  Needless to say, the looseness of the joints also makes the sufferer more prone to injuries such as sprains and even dislocations.  Joint Hypermobility Syndrome, itself, can also be a symptom of, or be caused by, more serious conditions, most of which are hereditary.  These include Ehlers-Danlos Syndrome, Marfan syndrome and Osteogenesis Imperfecta (brittle bone disease).

Ehlers-Danlos Syndrome

Ehlers-Danlos Syndrome (EDS) is a hereditary connective tissue disorder that affects the body’s processing of collagen and other proteins that interact with collagen.  There are many forms of EDS that vary in severity and the type of bodily structures that are affected.  Hypermobility EDS, also known as type 3 EDS, is now widely accepted to be the same condition as joint hypermobility syndrome.  It exhibits the same unusually large range of motion in the joints with less severe or noticeable skin symptoms, as compared to other forms of EDS.  Common symptoms include joint instability and chronic musculoskeletal pain as well as higher tendencies to have joint dislocations or subluxations (partial dislocations).

Marfan Syndrome

Marfan Syndrome is another hereditary connective tissue disorder.  It’s caused by a mutation in the genes that affects the production of a protein called fibrillin.  This causes parts of the body to stretch abnormally when placed under pressure.  It also causes some of the bones in the body to grow longer than normal.  The end result of this is that a person suffering from Marfan Syndrome is typically very tall and has very long arms, legs and fingers.  In more severe cases, their heart and eyes may also be affected.  Sufferers may develop heart defects or experience lens dislocation, a condition where the lens of the eye moves into an abnormal position.

Osteogenesis Imperfecta

Osteogenesis Imperfecta (OI), also known as brittle bone disease or Lobstein Syndrome, is a hereditary bone disorder that affects the bones and the connective tissue due to a deficiency in type-1 collagen.  To date, there are eight known types of OI with varying symptoms and levels of severity.  As the name suggests, people suffering from this condition have bones that are prone to fracture, are malformed, or both.  Another symptom of the condition is the blue-grey colouration of the whites of the eyes, known as the sclerae.  For some forms of OI, people may be diagnosed at birth but DNA testing may also be used for confirmation.  The relationship between this and joint hypermobility is slightly different, however.  While loose connective tissue may still be present in OI sufferers, the bones in joints may also become rounded, contributing to the increase range of motion.


Joint “popping” should also not be confused with crepitus, a medical term that refers to sound generated by the movement of joints.  While the definition may read similarly, crepitus is a different and far more worrying noise for joints to make.  It is normally felt through the skin, for example placing the palm of your hand over the shoulder joint and feeling the joint move.  But it can also be audible in some cases.  The worrying part is that it can be associated with or be a symptom of more harmful conditions such as partial joint dislocations, also known as subluxations, which can lead to damage to the joint.  It can also indicate joint instability or osteoarthritis that may generate noticeable amounts of pain for the sufferer.

What you can do

Joint conditions that affect the soft tissue are frequently hard to detect or diagnose.  So, it is possible that many people can unknowingly suffer from forms of joint hypermobility or ligamentous laxity that could be potentially harmful in the long term.  As with nearly every medical condition, early detection is important.

So, there are a few things we can look out for including swelling or pain in the joints, stiffness of the joints prior to, or after popping, frequent sprains, such as ankles or wrists and pain during normal movement of joints.

Should you experience any of the above symptoms, it is recommended that you speak to your doctor or physiotherapist as soon as possible.  Joint conditions are difficult to diagnose and MRI scans seem to be the main means of detecting soft tissue damage that X-rays cannot see.  Be sure to explain your symptoms to your doctor and avoid attempting to correct the issue yourself.