"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.
It's a catch-22 when you have knee pain from osteoarthritis. It hurts, so you don't want to move. But if you exercise, it can eventually make your knees feel better.
"I've gone a period of time when I haven’t moved a joint much and, when I first start, it's a little bit sore," says Denver physical therapist Eric Robertson, who has osteoarthritis. Robertson knows what it's like to be achy when he first starts moving. Your knee may hurt and ache, but it shouldn't keep you from doing your usual activities,...
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.