I've had it recommended to me by other people with small dogs, as well as those who do flyball, etc with their Border Collies. I'm planning on ordering the soft chews for Cali since she was diagnosed with luxating patellas and even though she never shows signs of pains, I hope to hold it off for as long as possible.
It won't fix the problem, but like a horse joint supplement, it will just help make the joint more mobile.
ETA: I would talk to your vet about the surgery and start by finding out what grade of luxating patella she has, most don't bother operating until it's grade four or the dog is in obvious pain... but if it's causing her pain already, I'd say it's past grade two or even grade three. There's a dog forum called chazhound.com/forums and people there should be able to give you great advice regarding luxating patellas and supplements.