Cracking in joints, first knees, now also elbows, wrists, shoulders..). x-ray ok. what is the cause, can it be fixed, what is prediction for future?

Not a problem: Cracking or popping sounds and sensations in joints is not a problem. The joints all produce small gas bubbles that cause this. Pain associated with this may be cause for a visit to your doctor. There are no future predictive issues with this, it does not mean you with develop arthritis at a greater chance than someone without these symptoms.

May be physiologic: you may need to see a rheumatologist for a definie diagnosis. We sometimes see this is very flexible people. ask you physician.