The injured was filling up the return duster in no. 4 entry 1 East. EE twisted to pick up another bag of rock dust and felt a tear on the inside of left knee. The area was dry and EE thought that their foot may have fouled under the frame of the duster. The accident occurred on 8-18-16, but EE continued to work. EE started missing work on 9-15-16 due to the injury. EE is still off.