INJURED STATED THAT A ROCK HAD FALLEN ON THE CANOPY OF HIS BOLTER. HE LET THE CANOPY DOWN & SWUNG IT AROUND TO SLIDE THE ROCK OFF WHEN IT FELL OFF. IT FELL THE WRONG WAS & HIT HIS LEFT LEG ON THE SHIN. HE WORKED THE REST OF THE SHIFT THINKING IT WAS JUST BRUISED. IT CONTINUED TO HURT & SOME SWELLING. HE WENT TO THE DOCTOR THE NEXT DAY& HAS A FRACTURE TO THE TIBIA.