Employee was operating a continuous miner in the #1 entry of the 002-0 mmu. He was sitting on his knees when a piece of draw rock approx. 3' long, 1' wide and 1"" thick fell and struck him on the left knee. He continued to work at his regular duties and did not seek medical attention until 4/19/05, at which time he was recommended for restricted duty until next dr's office visit.