Well...With all the buzz that physiologists make about how running, jumping, wheightlifting and many other activities are considered "high impact" and they tend to damage feet and knee joints, I would guess that by banging your articular cartilages against each other, even such tiny strikes, you´re damaging them...sorry for teh bad grammarMatias Almeida, Valencia, VENEZUELA.

I have read that there is not any apparent effect on the joints themselves, but finger strength is seriously reduced. I cannot understand why this is the case, as I would have thought no effect on finger strength and a definite deterioration in joint health was more likely, but then that is what science is about - testing things.

Even if you do no harm for yourself, think of other people. There are people and I happen to be one of them, who hates the sound of cracking bones. It is so disgusting!

I have read that there have been numerous studies on whether cracking your knuckles can cause arthritis or otherwise harm your hands, but there is still no consensus. Some studies suggest that you can snap your knuckles all you wish, and it won't cause osteoarthritis. But others indicate that repeatedly pushing a joint beyond its normal physical range when cracking, may damage the soft tissue around the joints, making your hand swell, and weaken your grip, (as mentioned above).Stretching or bending a joint, (actions that always precede a knuckle crack), causes the bones of the joint to pull apart slightly. This deformation decreases the pressure of the synovial fluid (that lubricates and nourishes the joint) which causes dissolved gases (oxygen, nitrogen and carbon dioxide) to form bubbles. As the joint gets stretched further apart, the pressure drops so low that the bubbles burst and a gas cavity with a partial vacume is formed. Medically it's called joint cavitation. The cavitation formation itself is silent, but part of the mechanism. Because there is gas from the cavitation on one side of the joint capsule membrane, when you suddenly distended the joint capsule, its membrane "snaps" (much like when you bring two ends of a piece of paper together and pull them apart quickly it "snaps") and the gas on one side of the membrane allows the snapped membrane to act like a drum, creating the cracking noise.It can take ~20 minutes for the gases to be reabsorbed. Perhaps these gasses play a role in cushioning the joint, or aiding nutrient uptake. So maybe it's more damaging to try to crack your joints again, when you've just done it, as they could be more susceptible to physical damage then. Some people have a larger separation between the bones and cracking is easier, and quite probably satisfying for them. But others joints can't relax enough to allow the bones to separate. To people who can't do it, like me, it seems like you must be applying serious force, or somehow you've loosened the joint over time to be able to do it. And that must mean damage, but actually it's just naturally easier for them to crack their joints. Tendons and ligaments also make cracking noises. For example, if your knee cracks when you stand up from sitting on the couch, you're likely hearing your tendons and ligaments popping into proper position around your knee's joints.

It's not just fingers and knees that crack. I had two separate whiplash injuries to my neck in traffic accidents about 15 years apart. Now my neck cracks most time I turn my head. My neck often becomes tired and tense, for example when I work at my computer. If I massage the bones in my neck I hear loud cracking noises and the tension and tiredness disappears in a matter of seconds. I guess this may be releasing the build up of gas bubbles that Emma described.