Employee was unrolling a 3"" water line on the surface area of the mine when he slipped and fell onto his left side and landed on his knee, causing it to twist. The employee, injured on 3-3-14, continued to work at his regular job and did not report the incident until 3-6-14. He was sent to Dr. on 3-7-14 and the Dr. placed employee on restricted duty until further evaluation.