EE stated that he was roof bolting in #9 entry where some loose shale was on the ground. He was installing the second row of bolts in this working place. He was walking towards the rear of the bolter when he stepped into a hole in the ground. EE cont. working until 3/5/10. EE stated he went to Dr. on 3/5/10 and was diag. with knee strain. He began missing 3/5/10.