Did the vet grade it? Luxating patellas are usually graded 1 to 4, with 1 being the least effected. This is when they tell you to have the dog rest to recover, and wait on surgery. I think around Grade 3, they recommend surgery.

Here is a link with good info for you!
http://www.bichonfriseusa.com/ref/luxpat/home.htm

Please don't worry that the link is for a bichon frise' site, that is just what I have for connections to all the online essays.

The surgery has a very high success rate. Hardest part is the 8 week recovery, when the dog must be on bed rest / crate rest. Once that is behind you, the dog is good to go!

I hope the info helps you.