I can't vouch for how it feels, but I've definitely heard the popping sound. I was running next to a teammate in college during some suicide sprint drills, and when he planted one leg at the baseline to turn back, his knee just went. And he hit the floor like he'd been shot. There was no trying to run it off. I think you're right. If it's a full tear, it's probably going to be evident right away. Thus concludes my medical opinion based on that one time I saw that one thing happen to that one guy I knew.
