The IE was in #10 entry to wash the rock dust out of the bed of a coal hauler. EE squatted down to pick up a water hose. As EE stood up EE turned to their left twisting and pushing off the right knee. During this motion EE felt something pop in their right knee. This incident resulted in a torn meniscus. The incident occurred on 01/12/2016. IE started missing work on 01/20/2016.