Has anyone on this forum tried Alexander Technique? (Its not for joint cracking, but that can be a benefit!) I used to have lessons, in fact I got so keen I started doing the training to be an AT teacher. Your body changes amazingly - the training is three years but for various reasons I gave up after a couple of terms. Once, while I was having a lesson, my usually stiff upper back gently (and fairly quietly) all let go clicks rather than cracks. It reminded me of a scrunched up ball of cellophane releasing. I felt suddenly taller.
At the teacher training course, a few of us found wed begun to have aching hip joints, with a feeling in the lumbar region that something wanted to give. A few days later, one of the students was lying in semi-supine position on one of the teaching tables and her lower back gave a loud crack the table made the noise resonate. Then a few days later the same thing happened to me it was one of the most satisfying cracks Ive ever had. Unfortunately it never happened again.