Qs: clicking/popping joints without pain

i bet anyone or most experience this.

to the 'elderly' (sorry, for the lack of a better term), have you experienced any pain as you have gone along?

i've been experiencing popping shoulders, elbows, knees, hips from random movements, ie i cannot replicate them. at times they pop, at times they don't, but none of them show any signs of pain.

what are these? sign of aging? symptom of something? or are they merely signs of 'unused' joints? i haven't had any injuries though...