THE ROOF BOLTING CREW WAS BOLTING THE FIRST CUT IN THE RIGHT CROSSCUT OFF THE BELT ENTRY. THE INJURED EMPLOYEE WAS OPERATING THE RIGHT SIDE OF THE MACHINE. IN POSITIONING THE DRILL HEAD TO INS TALL A RIB BOLT THE CANOPY CONTRACTED AND DISLODGED COAL AND ROCK STRUCK EMPLOYEE'S LEFT CALF AND BACK OF KNEE.