EE was walking along the #4 unit FCT low framing when he stepped on a piece of slick draw slate. He slipped and twisted his left knee. He continued working, notified the mine on 1/5 he would see his doc on about 1/8 to have his knee checked out to continued knee pain. He had surgery on 3/5 for a menisci tear of his knee. His 1st scheduled work day missed was 3/5/10.