An employee was using a chainsaw to cut an oak tree that had been damaged in a storm. The employee had cleared the area and cut the tree to a knee-high height. He began to saw a limb that measured approximately 8-10 inches diameter and 10 feet long. While sawing the limb, he noticed it was about to fall and stepped backward. He lost his footing just as the limb came loose. The limb landed on his left leg approximately 6-8 inches above his ankle, pinning his lower leg and resulting in a broken bone that required hospitalization and surgery. The employee was wearing personal protective equipment at the time of the incident.