If it is a partial ACL tear, I would start now to limit all activity for the next 10 days, until you go back to your Vet, only out for potty breaks on a leash. No walks, no steps, no getting on the couch, no excitement / moving around, no getting in the car, crate if possible. I know this sounds extreme, but my first Greyhound had a partial tear and this is what the Vet told us to do. We did this for 8 weeks and 4 more weeks of no running and she healed fine with no surgery and no problems later. When you go back in 10 days, ask your Vet about the resting versus surgery.