The knuckles are the
joints of the
finger
A finger is a limb of the body and a type of digit, an organ of manipulation and sensation found in the hands of most of the Tetrapods, so also with humans and other primates. Most land vertebrates have five fingers ( Pentadactyly). Chamber ...
s. The word is cognate to similar words in other Germanic languages, such as the Dutch "knokkel" (knuckle) or German "Knöchel" (ankle), i.e., ''Knöchlein'', the diminutive of the
German
German(s) may refer to:
* Germany (of or related to)
**Germania (historical use)
* Germans, citizens of Germany, people of German ancestry, or native speakers of the German language
** For citizens of Germany, see also German nationality law
**Ge ...
word for bone (''Knochen''). Anatomically, it is said that the knuckles consist of the
metacarpophalangeal[Utah Mountain Biking]
Thumb Sprain
First as metacarpo. (MCP) and
interphalangeal (IP) joints of the finger. The knuckles at the base of the fingers may be referred to as the 1st
or major knuckles while the knuckles at the midfinger are known as the 2nd and 3rd, or minor, knuckles. However, the
ordinal terms are used inconsistently and may refer to any of the knuckles.
Cracking
The physical mechanism behind the popping or cracking sound heard when
cracking joints such as knuckles has recently been elucidated by cine
MRI to be caused by
tribonucleation
Tribonucleation is a mechanism that creates small gas bubbles by the action of making and breaking contact between solid surfaces immersed in a liquid containing dissolved gas. These small bubbles may then act as nuclei for the growth of bubbles w ...
as a gas bubble forms in the
synovial fluid
Synovial fluid, also called synovia, elp 1/sup> is a viscous, non-Newtonian fluid found in the cavities of synovial joints. With its egg white–like consistency, the principal role of synovial fluid is to reduce friction between the articul ...
that bathes the joint. Despite this evidence, many still believe it to be caused by synovial fluid filling the vacuum left by the joint's displacement. In 2009, Donald L Unger was awarded the
Ig Nobel for Medicine for his informal experiment with knuckle cracking. For 50 years, he cracked the knuckles of one hand while not cracking the knuckles of the other during that time. He self-reported no issues with arthritis on either hand.
[Does knuckle cracking lead to arthritis of the finger]
/ref>
Gallery
Knuckles.jpg, Clenched fist with knuckles (encircled in red)
MotorcycleRacingGlove.jpg, Motorcycle racing gloves with titanium knuckle protectors
See also
* Metatarsophalangeal joints, also informally known as toe knuckles, the equivalent joints in the toes.
References
{{1911, wstitle=Knuckle, volume=15, page=883
Fingers