The night of 2-20-13 a winter storm left snow and ice at the quarry. After the morning meeting on 2-21-13, employee proceeded to walk towards mobile equipment using a set of steps that were ice covered. Holding onto hand rail he fell twisting left knee. Employee worked but knee kept bothering. Work comp approved an MRI on 3-25-13 MRI results shows a tear at dr appt on 4-2-2013.