My ACL… :(

How can you tell if you sprained it or if there's a tear? I woke up from pain and while I can bend it and bear weight, it really hurts. I'm sad because I have a race on Saturday but even more worried that this might be a tear. :(

ETA: After acemetacin and a few hours, I have my full range of motion back but man, I am sore-especially when I first stand up. I'm thinking this is a sprain or very minor tear from when I tried to stabilize myself during a slip last night. It didn't hurt when it happened but was super painful several hours later. No more running for 7 days, I'll be icing it and hopefully it'll feel better by then. If it's still sore after a few days, I'll try and see a doctor.

Dammit, loose joints in pregnancy, slippery sidewalks, and previous knee injuries that have made me super paranoid.