The question: I often crack my knuckles to the horror of my girlfriend who thinks that beyond the gross factor that I'll get arthritis if I keep doing it. Are there really any harms to cracking knuckles?
The answer: Despite the many cautionary tales, there isn't great evidence to support the claim that knuckle-cracking causes long-term damage on the joints.
The knuckles are the joints between the fingers and hands. Like every joint in the body, the knuckles contain a thick clear lubricating substance called synovial fluid. Within this fluid, there are gases such as oxygen, nitrogen and carbon dioxide. When we crack our knuckles, we're pulling apart the two bones that surround the joint, decreasing pressure in the fluid, which releases these gases in the form of bubbles. This release and popping of the bubbles causes the cracking sound.
In those who suffer from arthritis, the joint can also make sound with movement due to bone damage or loss of the cushioning cartilage in the joint spaces.
If you have pain, swelling or see redness over the joints, it may indicate that there is an underlying abnormality involving the bone, cartilage or ligaments.
While there have not been large scale studies on this topic, the smaller trials have shown no correlation between knuckle-cracking and arthritis in the hands.
So what does cause arthritis? Well-established risk factors include age, a family history of arthritis, or if there has been a previous traumatic injury to the joint (i.e. from sports, or an accident). Being overweight can put significant stress on our lower joints such as the hips, knees and ankles, and also predispose us to the condition over time.
Dr. Sheila Wijayasinghe is the medical director at the Immigrant Womens' Health Centre, works as a staff physician at St. Michael's Hospital in their Family Practice Unit and at Hassle Free Clinic, and established and runs an on-site clinic at Women's Habitat Shelter in Etobicoke. Follow her on Twitter @DrSheilaW