EMPLOYEE GOT OFF OF HIS LOADER TO RETRIEVE A PIECE OF METAL THAT HE SAW IN THE MATERIAL BEING LOADED. AFTER HE RETRIEVED THE PIECE OF METAL HE WAS DESCENDING DOWN THE PILE OF MATERIAL. HE LOST HIS FOOTING AND HIS FOOT FOLDED UP BEHIND HIS LEG THUS CAUSING HIS KNEE TO POP. PAIN WAS FELT IN THE KNEE WHILE WALKING.