An employee was pumping lightweight gypsum flooring into a room on the second floor. The employee then went to help another individual who was trying to remove a sheet of drywall from the middle of a stack of 1/2 inch plywood that was leaning against a wall. As the other individual pulled out the sheet of drywall, approximately 14 sheets of plywood fell over onto the injured employee, resulting in a lateral tibial plateau fracture and lateral meniscus tear of the left knee.