I have a 11 and half year old labrador. Generally active. He did manage to tear his right rear leg ligaments couple of years ago and had to undergo major surgery. He has had some limp in the right rear leg sine surgery. Since last two three days he has been very very quite and just about lying in one place. Even hesitant on getting up and going out to pee and/or potty. This morning, he just could not get up on his own and after help when he walked, he was tripping from rear side of body. Very difficult to maintain balance. I think that pain is to the point where he is even not willing to to get and get water, I almost had to feed him with my hand. Couple of time when I took him out in lawn, he did come out after lot of hesitation but seems to not have good control and is tripping. Have given him analgesic pain reliever. I will take him to doctor tomorrow but I am sure he will do a whole set of very expensive checks. Any advise/help.

Let the vet decide what is best for the dog. Unless it is a temporal infection it could well be that the dog is simply at the end of his line... Prepare you for that possibility. Are you willing to go through all these possible expenses for an 11 and a half year old dog?