Andriy Popov/Alamy
How can popped knuckles be so exceptionally loud? (continued)
Marthinus Roos
Elgin, Moray, UK
The surfaces of human joints fit against each other very well and have rims of synovium, the membrane lining of the joint. Together, these form a very effective suction cup, which work together with the surrounding ligaments and thickening in the fibrous “sacks” around the joints, known as joint capsules, to hold the bones of the joint in the correct place and orientation.
When a distraction force (such as pulling on a finger) is applied, the ambient pressure in the surrounding tissues, which is equal to…
