My boy wasn't treated for 18months because he only had a partial tear (vets choice), he's 32kg. When the cruciate eventually did tear completely it was discovered that he had a fair bit of damage to the meniscus and the start of rather bad arthritis in that joint.
I would always recommend getting the operation ASAP

If the cruciate has completely ruptured, it can't mend itself. As was explained to me, the joint will always be unstable, and will get more and more arthritic and the dog will be in increasing pain. It will probably cause damage to the meniscus, and put strain on the other limbs as the dog tries to compensate.

When I looked at the alternatives to surgery, they did not seem to offer any improvement to the dog's comfort, and risked the dog being in more pain. The only thing that looked like it may make some sense was a really well fitted brace for the leg...but you are talking quite a lot if money, and no guarantee of any long-term improvement.

If they really won't operate, then they must pay for pain relief.

Somebody posted this link before ...
http://www.tiggerpoz.com/

It says carefully restrict the dogs activity for 8 weeks. I did for 3 weeks and the good leg ended up with a complete rupture. My dog could hardly walk and looked like she had severe HD so from personal experience i would now take that article with a pinch of salt. Not saying it might not work for someone with a small dog but not with large i'm afraid.

I know what you mean. If I had the money I would pay for the dogs op myself but unfortunately I don't. My dog had the op himself over a year ago at 12 and is back to normal. This dog is only 7 She has been like this for quite a few months now and while she isn't as bad as she was, she puts a bit of weight on it before she was on 3 legs all the time. But as others as said it gets a bit better before it gets worse and then theres the danger of the other leg doing the same. I will talk with them, its not like they havent got money. They are planning a 6 week trip to Australia at the end of the year!