In Calhoon v. Lewis (2000) 81 Cal.App.4th 108, the plaintiff suffered injury when he fell off his skateboard and hit a metal pipe protruding from a planter in the defendants' driveway. Finding the primary assumption of risk doctrine barred his claims, the court rejected the plaintiff's argument that the concealed metal pipe increased his risk of harm: "The plaintiff was injured because he fell. As he concedes, falling is an inherent risk of skateboarding, and the presence of the pipe or the planter had nothing to do with his falling down. The fact that his injuries were more severe than they would have been if the pipe had not been in the planter does not make the assumption of risk doctrine inapplicable. The Knight exception (Knight v. Jewett (1992) 3 Cal.4th 296) applies when the defendant increased the risk of injury beyond that inherent in the sport, not when the defendant's conduct may have increased the severity of the injury suffered." (Id. at p. 116.)