EMPLOYEE WAS OPERATING A FLETCHER ROOF BOLTER. HE REACHED TO HIS LEFT TO GET A ROOF BOLT AND STEPPED ON A LUMP OF COAL AND HIS LEFT LEG AND KNEETWISTED CAUSING HIM TO FALL. HE CALLED TO THE OT HER ROOF BOLTER WHO GOT FURTHER HELP TO GET HIM OUT OF THE MINE. INJURY DID NOT INVOLVE ANY ASPECT OF COMPLIANCE WITH RULES OR REGULATIONS OR JOB SKILLS TRAINING.