Editing Crepitus (section)

==Causes==
The sound can be created when two rough surfaces in an organism's body come into contact—for example, in [[osteoarthritis]] or [[rheumatoid arthritis]] when the [[cartilage]] around joints erodes and the surfaces in the joint grind against one another, or when the two [[Bone fracture|fractured]] surfaces of the broken [[bone]]s rub together. Crepitus is a common sign of [[bone fracture]].

Crepitus can easily be created and observed by exerting a small amount of force on a joint, thus '[[cracking joints|cracking it]]'. This is caused by bubbles of [[nitrogen]] forming in the [[synovial fluid]] bursting. Almost every joint in the body can be 'cracked' in this way, but the joints which require the least amount of force to produce this effect include the [[Toe#Hallux|hallux]] (big toes), the [[knuckle]]s and the neck joints. This phenomenon is caused when the movement of the joint lowers the pressure of its synovial fluid, causing the bubbles to form and burst. A [[Refractory period (physiology)|refractory period]] of about 20 minutes exists where the joint cannot be stimulated to produce crepitus after being cracked until the nitrogen gas dissolves back into the synovial fluid.<ref>{{Cite web |date=2018-03-29 |title=Simulation May Finally Explain Why Knuckle Cracking Makes That Awful Sound |url=https://gizmodo.com/now-we-know-why-knuckle-cracking-makes-that-awful-sound-1824154323 |access-date=2023-10-30 |website=Gizmodo |language=en}}</ref>

In soft tissues, crepitus can be produced when gas is introduced into an area where it is normally not present.

The term can also be used when describing the sounds produced by [[lung]] conditions such as [[interstitial lung disease]]; these are also referred to as "[[rales]]". Crepitus is often loud enough to be heard by the [[human ear]], although a [[stethoscope]] may be needed to detect instances caused by [[respiratory]] diseases.

In times of poor surgical practice, post-surgical complications involved [[Anaerobic organism|anaerobic]] infection by ''[[Clostridium perfringens]]'' [[strain (biology)|strains]], which can cause [[gas gangrene]] in [[Tissue (biology)|tissues]], also giving rise to crepitus.

Subcutaneous crepitus (or surgical emphysema) is a crackling sound resulting from [[subcutaneous emphysema]], or air trapped in the [[subcutaneous tissue]]s.