Off and on for the past few months my sternum/breastbone has been popping . It sounds about the same as a loud knee pop when it happens, and over the past 2 weeks has really increased in frequency. It happens when I get up from sitting, or try to lay down on my back, reach my hands above my head etc.. It is somewhat painfull, sort of a sharp stabbing sensation, thankfully, the pain doesn't last long. Do any of you experience this? Is this a Lupus related, or costochondritis related thing or something unrelated?