Crepitation: Why do joints crack, and should you be concerned about it?

Joints often produce a wide range of sounds, from clicks to creaks. The scientific term for this phenomenon is crepitus, derived from the Latin word crepitus. It is common among people of all ages, although it becomes more prevalent with age. But what causes such an unusual effect?

The most frequent cause of crepitus is the formation of air bubbles at the joint interfaces. These bubbles typically develop where a layer of fluid separates two bones, reducing friction between them. Joints can expand and contract both during everyday body movements and during specific activities. When this occurs, the low pressure in the joint space causes gases from the natural 'lubrication' of the joints to form a cavity – this usually contains oxygen, nitrogen, and carbon dioxide.

People often tend to believe that joint cracking is a concerning symptom, although this is not always the case. In 2015, researchers examined joints in real-time and demonstrated that gas bubbles are quite neutral. Moreover, after the first loud crack, gases require some time to build up again – which is why you can't crack your joints too frequently.

Additionally, individuals with hypermobile joints can move their joints far beyond normal ranges of motion. This stretching of the joint capsule also creates a cavity where gas accumulates. This syndrome is hereditary, so children often crack their joints just as well as their parents.

Sometimes, the noise has an anatomical cause. It occurs when tendons move over uneven structures of the bones to which they are attached, and then quickly return to their original position. A common example is the cracking sound in the knee when transitioning from a sitting to a standing position or when climbing stairs.

So, should you really not worry when your joints make loud noises? Not necessarily. Cracking can also occur when the cartilage layer between the bones wears down or becomes damaged. In this case, the cracking is accompanied by painful sensations, as the bones are essentially rubbing against each other. Worldwide, 50% of people over the age of 65 suffer from osteoarthritis. Pain from osteoarthritis can be managed in various ways, but it is important to consult a specialist.

In conclusion, it is worth noting that noisy joints themselves do not pose any threat. For instance, antelopes even use this sharp sound to scare off predators. However, any noise that comes from a joint over an extended period is a good reason to see a doctor and check your health.