If it is not possible for him to fix the kneecap, eventually the dog will develop arthritis in the joint and will either walk with three legs or may even have to drag her end. You might look into a wheeled cart that supports the hind end, similar to that which is used when Dachshunds undergo back surgery and are no longer able to walk.
I have seen some dogs that no one is able to repair. As long as they are small breeds, the owner just has to make adjustments. It is very difficult when the dog is large and not able to be carried around.
If you would like to look down at the comments section and there is a Facebook link with a video of a small dog that is so severely affected that surgery is not an option.