Why do our bones creak? Physiotherapists explain.

Cracking your fingers , feeling a "crack" in your knee when bending over, or hearing your back or neck creak when stretching in the morning... We've all experienced it. It's not a new phenomenon: as early as the 19th century, British doctors were observing "spontaneous popping" in joints .

Since the rise of chiropractic at the end of the 20th century, sound has been associated with restoring bodily balance. These sounds, associated with relief or discomfort, have also become prominent in the digital world. Millions of people watch videos on social media showing joint creaking in real time, almost as if they were special effects of the human body.

But what is that sound really about? Is it dangerous? Why does it fascinate us so much?

Contrary to popular belief, when we crack our fingers or hear a crack, it's not bones hitting each other. That characteristic sound comes, in most cases, from the synovial joints, which are surrounded by a capsule containing synovial fluid .

When a joint is moved quickly or forcefully, a sudden decrease in pressure occurs within the joint capsule, causing the sudden formation of gas bubbles . This phenomenon is called joint cavitation. Magnetic resonance imaging (MRI) research shows that the sound occurs during the formation of the bubble, not during its collapse, which would challenge previous theories.

When we hear a cracking sound in a joint, it's not a bone "popping back into place" or a dislocated joint. What we're actually hearing is the result of a biomechanical process called cavitation , which is common in healthy people and is generally harmless.

However, not all joint sounds are benign. If the popping sound is accompanied by pain, locking, weakness, or instability, it could indicate a pathological condition such as chondropathy , a meniscal injury, or joint hypermobility. These situations require evaluation by a healthcare professional.

For decades, the belief has been widespread that the habit of cracking your fingers could lead to joint wear and tear or even osteoarthritis. This idea has been repeated countless times in family conversations, during medical consultations, and even in the press.

However, scientific evidence does not support this. In fact, a study published in The Journal of the American Board of Family Medicine (2011) analyzed more than 200 older adults and found no relationship between finger cracking and the presence of osteoarthritis in the hands.

However, although cracking your fingers does not cause structural damage or osteoarthritis, doing it compulsively or aggressively could irritate the soft tissues surrounding the joint , such as ligaments or tendons .

Furthermore, although the gesture seems harmless from a medical perspective, it is not always pleasant for those who hear it, and can even generate some discomfort or become a source of conflict.

In physiotherapy, osteopathy, and chiropractic, some manual techniques commonly produce a joint sound, or cavitation. This sound is often interpreted as a guarantee of therapeutic success by both practitioners and patients. However, evidence indicates that sound alone does not guarantee the effectiveness of the technique nor does it imply a true biomechanical correction.

Furthermore, it has been shown that manipulation can be effective even when no sound is produced, and that an audible crack may not be associated with significant clinical improvements. Therefore, joint sound during manipulation should not be considered a reliable marker of efficacy.

The therapeutic benefits of joint manipulation appear to be related more to neurophysiological mechanisms such as reflex muscle relaxation from manual therapy than to the actual cracking.

It's common to see platforms like TikTok, YouTube, and Instagram saturated with videos of joint adjustments where strategically placed microphones amplify the creaking sounds, generating millions of views. This content fuses clinical aesthetics with entertainment, offering a sense of "instant body fix."

However, the show carries significant risks. Consuming medical content on social media that isn't sourced from healthcare professionals can foster unrealistic expectations about treatments and promote simplified or passive approaches to complex musculoskeletal problems.

It's important to note that this type of content can reinforce reliance on passive techniques and minimize the value of active movement, education, and therapeutic autonomy. The key to good musculoskeletal health is not sound, but movement . Treatment for back, neck, or joint pain should not be based solely on passive techniques (such as manipulation or massage), but rather on active strategies that accelerate recovery and help manage pain.

This article was originally published on The Conversation .