EE STRAIGHTENING YIELD SIGN, HAD BOTH ARMS AROUND SIGN WHILE APPLYING PRESSURE. AS EE WAS APPLYING PRESSURE, SHOULDER POPPED. RELEASED PRESSURE FROM AROUND SIGN AND MOVED ARM AROUND TO SEE IF IT WAS HURT OR A ""NORMAL POP"", WAS JUST A LITTLE SORE. COMPLETED TASK & TOOK SOME IBUPROPHEN. REPORTED INCIDENT NEXT MORNING