I am a long time multiple joint cracker, first-time poster…
In my late teens/early twenties I realized that I was capable of cracking my ribs. This at first was rare, but now I can pretty much do it at will. I practice yoga, so I am pretty flexible -- if I bend backwards with my arms outstreched over my head one or a few of the joints at my sternum (front/middle of my ribcage) will pop ever so slightly. Sometime, on a very rare occasion, just taking a dep breath, puffing out my ribs, has caused this too.
Can anyone else do this?
Oh, I just tried and it worked -- it was a small quite one. In any case, I think this is my favorite joint to crack since it seems so unique.