After stepping down from a 2'ladder, the ee turned and felt a pop in his right knee. EE was seen by the Dr. on 04/25/2014. A causation investigation was launched at company's request. The ee underwent surgery to right knee on 09/29/2014. On 12/29/2014,company received causation findings stating that an acute on chronic injury meeting the 1% WC causation requirements occurred.