Is cracking the knuckles safe?

My husband who incidentally is a medical doctor enjoys cracking his knuckles. Apart from the noise of the cracked knuckles which is annoying, I read somewhere that the habit may also lead to arthritis of the finger joints, a claim my husband refutes. Please let me know whether or not it is safe to crack one’s knuckles and what I can do to make my husband stop the annoying habit.

Chinwe (by SMS)

EFCC has not contacted me on any probe — Ambode

The “pop” of a cracked knuckle is caused by bubbles bursting in the synovial fluid — the fluid that helps lubricate joints. The bubbles pop when you pull the bones apart, either by stretching the fingers or bending them backward, creating negative pressure. Cracking your knuckles may aggravate the people around you, but it probably won’t raise your risk for arthritis. That’s the conclusion of several studies that compared rates of hand arthritis among habitual knuckle-crackers and people who didn’t crack their knuckles. Even if knuckle cracking doesn’t cause arthritis, there’s still good reason to let go of the habit. Chronic knuckle-cracking may lead to reduced grip strength. And there are at least two published reports of injuries suffered while people were trying to crack their knuckles.