HE STATED THAT AS HE WAS OBSERVING THE MINE ROOF, HE ATTEMPTED TO STEP UP ONTO THE WALKWAY OF THE ROOF BOLTING MACHINE. HE TRIPPE ON THE REAR HITCH AND FELL ONTO THE WALKWAY, HITTING HIS RIGHT KNEE ON THE WALKWAY. IT WAS DIAGNOSED AS AN ""AVULSION OFF THE SUPERIOR POLE OF THE RIGHT PATELLA"" (FRACTURE).