What Causes Mild Pain And Popping Sensation Under The Right Rib?

Very weird movement on my bottom right rib, Almost like as though I can move the bottom rib. It feels like a popping motion. I can only do it when sitting in the right position, and there is very little pain involved. I am 5 foot 9 inches roughly and weigh 280 pounds. Don t know if this has an effect on this though I would believe it could.