Oh they can definitely rupture the ACL just playing around. Jumping up, turning too quick, all the things that dogs do on an every day basis. LOL I know if Hazel gets the zoomies, I am cringing the whole time because I am always conscious of her knees. She definitely learned what "EASY! Careful of the big owie!!" meant....she heard it over and over and over again.
It's good that your team captain has experience with ACL ruptures, she'll know what to watch for that could be an unnecessary risk.
Livin in a Newfie Drool Zone