That impressive noise is caused by popping gas bubbles in the fluid surrounding the joints. It can, admittedly, feel satisfying (and even macho).
The substitute: Distract your child by giving him some Bubble Wrap to pop, then send him to another part of the house.
Also try: Finger exercises can be a quiet alternative to cracking, according to Greg Irwin, a finger-exercise expert (!) and the creator of the Finger Fitness Program. “They help develop strength and dexterity,” he says. “Tell your kid they’re like push-ups and sit-ups for your hands.” Try finger bends: Press hands together, then gently bend all fingers over to the left, then to the right. (See more at handhealth.com.)
More drastic measures: If the problem persists, establish no-cracking zones, like the dinner table. But don’t worry that your child is in for a whopping case of arthritis someday. One dedicated researcher, Donald Unger, M.D., published a study in Arthritis and Rheumatism in which he cracked only his left knuckles daily for 50 years and found no noticeable difference between his two arthritis-free hands.