"Cracking joints" and "popping knuckles" are an interesting and poorly understood phenomenon. There are many theories as to why joints crack or pop, but the exact cause is simply not known.
Painless cracking of joints is -- as a rule -- not harmful. However, common sense generally would suggest that the intentional and repetitive cracking of one's joints not only is potentially socially bothersome but also could be physically troublesome when it produces pain.
Just as the tread on your tires wears away over time, the cartilage that cushions your joints can wear away, too. It's a condition known as osteoarthritis. And without enough cushioning, the bones of a joint will hurt when they rub against each other.
Frayed cartilage can't heal or grow back. "There's no way to reverse the arthritis once it has started," says Michaela M. Schneiderbauer, MD, an orthopedic surgeon at the University of Miami Miller School of Medicine. But there are ways to reduce the...
Knuckle "cracking" has not been shown to be harmful or beneficial. More specifically, knuckle cracking does not cause arthritis.
Joint "cracking" can result from a negative pressure pulling nitrogen gas temporarily into the joint, such as when knuckles are "cracked." This is not harmful. "Cracking" sounds can also be heard if tendons snap over tissues because of minor adjustments in their gliding paths. This can occur with aging as muscle mass and action change.
If cracking is accompanied by pain, there could be underlying abnormalities of the structures of the joint, such as loose cartilage or injured ligaments. Some patients with arthritis (inflammation of joints, usually painful), bursitis, or tendinitis notice "cracking" sounds due to the snapping of irregular, swollen tissues.