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.
Cracking of joints, also referred to as “popping”, is a form of joint manipulation that produces a popping or cracking sound, as may occur during knuckle-cracking, a deliberate action.
People can crack several joints in their bodies, including the hips, wrists, elbows, back and neck vertebrae, toes, shoulders, feet, jaws, ankles and Achilles tendon.
Does cracking one's knuckles cause arthritis?
Researchers from the Uniformed Services University of the Health Sciences, Bethesda, Maryland, USA, carried out a study – “Knuckle Cracking and Hand Osteoarthritis” – published in the Journal of the American Board of Family Medicine (April 2011 issue).
Senior author, Kevin deWeber, MD, FAAFP, USUHS, explained that previous studies had not shown a link between knuckle cracking and hand osteoarthritis. One study, however, suggested an inverse correlation between knuckle cracking and metacarpophalangeal joint (knuckle joint) osteoarthritis.
Dr. deWeber and team set out to determine whether knuckle cracking might be linked to hand osteoarthritis. They carried out a retrospective case-control study involving 214 people, of whom 135 had radiographically proven hand osteoarthritis and 80 did not (healthy controls). The participants were aged from 50 to 89 years; they had all received a radiograph of the right hand during the previous five years.
The researchers gathered data on the participants' frequency, duration and details of their knuckle cracking behavior, as well as any known risk factors for osteoarthritis of the hand.
Dr. deWeber and team found that:
- 20% of all the 215 participants cracked their knuckles regularly
- 18.1% of those who cracked their knuckles regularly had hand osteoarthritis
- 21.5% of those who did not crack their knuckles had hand osteoarthritis
The researchers said the difference in the prevalence of osteoarthritis between the knuckle crackers and non-knuckle crackers was not significantly statistically different.
The authors wrote:
“When examined by joint type, knuckle cracking (KC) was not a risk for OA in that joint. Total past duration (in years) and volume (daily frequency ‘- years) of KC of each joint type also was not significantly correlated with OA at the respective joint.
A history of habitual KC – including the total duration and total cumulative exposure'”does not seem to be a risk factor for hand OA.
Can chronic knuckle cracking reduce grip strength?
Two researchers, J Castellanos and D Axelrod, from the Department of Internal Medicine, Mount Carmel Mercy Hospital, Detroit, Michigan, USA, wrote in Annals of Rheumatic Diseases (May 1990 issue) that “habitual knuckle crackers were more likely to have hand swelling and lower grip strength”.
They investigated the association of habitual knuckle popping with hand function on 300 patients aged at least 45 years. None of them had evidence of neuromuscular, inflammatory or malignant diseases, factors associated with lower grip strength and hand osteoarthritis.
Seventy-four of the participants were habitual knuckle crackers while 226 were not.
They found similar rates of hand osteoarthritis in both groups. They also linked habitual knuckle cracking to nail-biting, smoking, drinking alcohol and manual labor.
The authors concluded that habitual knuckle cracking results in functional hand impairment but not hand osteoarthritis.
Dr. Donald Unger spent over sixty years cracking the knuckles of his left hand but never his right. He reported no arthritis or other problems in either hand. He earned the Ig Nobel Prize in Medicine for this in 2009.
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. Knuckle “cracking” has not been shown to be harmful or beneficial. More specifically, knuckle cracking does not cause arthritis.