When a chiropractor adjust someone, he has a lot of training to make sure it’s done properly and that no harm will be done. Also, the theory is that a chiropractor adjusts a “restricted” or “hypomobile” joint. This is a joint with a decreased range of motion that needs to be corrected. Somebody who adjusts or “cracks” their own joints over, and over, and over, are creating a hypermobile joint that becomes unstable over time. This unstable joint tried to correct itself by growing bone spurs and creating arthiritis in the joint. So there is such thing as “too much of a good thing”. I am not aware of any good long-term scientific studies that supports this theory. However, in case it’s true, and for safety reasons, please “do not try this at home” and leave it to the professionals.