In the last few months I found, for the first time, that I get an occasional crack right at the ball joint where my left femur meets the pelvis. This first time it happened in the shower as I had my left leg propped up and moved it to the right side. It was surprising. Since that first time I'm finding that I get this crack about once every few days to couple weeks or so. Sometimes it happens in the shower like the first time, and sometimes it happens during the day while sitting down -- it will feel ready and will happen when I pull the left thigh sideways. It is an infrequent crack -- but when it happens it is a deep, enormous, loud, profound crack. It is an amazing feeling and just feels like so much pressure and tension is being released, so I look forward to getting it back each time. It seems interesting that I'm only getting this on one side of the body as of now, and that it started sort-of arbitrarily.