In Georgia, a defendant asserting an assumption of the risk defense must establish that the plaintiff: (1) had actual knowledge of the danger; (2) understood and appreciated the risks associated with such danger; (3) voluntarily exposed himself to those risks." "Knowledge of the risk is the watchword of assumption of risk, and means both actual and subjective knowledge on the plaintiff's part." Hillman v. Carlton Co., 240 Ga. App. 432, 433 (1) (522 SE2d 681) (1999).