Employee was working night shift on 2/7/11.While pulling drill steel out of muck pile, he experienced pain in his left knee. He went to medic at end of shift(am on 2/8/11). At this time, it was a ""RO"". Since this time, the knee has not been getting better, he finally went to Doctor & surgery was set for 12/21/11. 1st shift missed on 12/25/11.