Please help... I really need some help

I have a question about a disease my baby Yorkshire Terrier has that the vet just found out my baby has had since hewas born!!! He has Luxating Patella class 4!!! Theres only 2 options for him expensive surgery that might not even work or ammputation!!! I was wondering if any of your babies have gone through anything like this and what you decided to do!! I am just a mess... I just need some help and suggestions????