Welcome Gina and of course, Shelby!

If your gonna have to get cancer in a leg, too bad it wasn't the torn ACL one! 

Yes, I had two ACL repairs with a three legged dog.  I had the TPLO where the metal plates are attached to the bones.  Is that what you are referring to?  I've never heard of a knee replacement for ACL tears, but I'm no expert!

If Shelby is walking/bouncing/hopping at all, then I'd be very encouraged! 

Comet was born with a deformed front leg  that was useless. When Comet's back knee when out, she got up and went right back down.  She couldn't walk because her back knee was so unstable.  When the other one went out a couple of years later, which is common - again, she went down again. 

When I had a 4 legged dog have hers go out, she held her leg up and wouldn't walk on it at all.

I don't know for sure since I'm not a medical expert, but I would assume that no surgeon is going to recommend surgery for Shelby unless she isn't able to walk at all. They'd probably take a conservative crate rest approach.  Maybe Dr. Pam DVM can jump in and give you her medical opinion.

Dang, knee surgery is cheap where you are!  I live in Nevad and an experienced ortho surgeon came in and performed the TPLO on Comet and I think the total bill was around $3500.  The surgeon I think charged $1500 or $1700 and the rest was my vet and the surgery stuff. 

I hope with all my heart Shelby won't need a future surgery since it is an extremely hard and long recovery.  For a 3 legged dog to become 2 legged, it was tough.  And Comet weighed just under 40lbs, so we could actually carry her.  But even carrying 38lbs after 12 weeks can take it toll on you!

Best wishes for a quick recovery for Shelby!