EMPLOYEE STATED THAT HE HAD PARKED HIS COAL HAULER AND WAS WALKING IN NO. 3 ENTRY TO CHECK HIS TRAVEL ROUTE FOR THE NEXT PLACE TO BE MINED. HE STATED THAT AS HE WA WALKING THAT HE STEPPED IN A HOLE IN THE MINE FLOOR THAT CAUSED HIS KNEE TO BENT BACKWARD AND TWISTING HIS KNEE.