Scott Caan, who played Daniel Williams in Hawaii Five-0, was forced to return back to the US mainland when he aggravated an old knee injury. The production team and Scott himself were not going to let that get in the way; instead, they decided to write Danno’s injury into the script.
That’s why in the episode “Lanakila,” Danno is asked about his injuries by Dr. Teddy, and Danno, standing next to Steve, responds, “This guy is like a physical injury, Doc. Ah, 10 minutes after meeting him, I get shot and blasted backwards through a window, okay? A few hours after that, he drives a car — not joking — onto the deck of a Chinese freighter ship. And, yes, I was in it. The car, not the ship.”