The EE was operating a coal hauler. He stated that he was walking on the unit and felt pain in his left knee on 8/1/14. He continued to work up until Aug 8, 2014. He was taken off work on 8/11/14. He had left knee arthroscopy on 8/20/14. A postoperative report received on 8/25/14 along with the attached information indicated wear and tear and degeneration in his left knee.