
My lurcher had two damaged cruciates. In his case it was degenerative (possibily due to hypothyroidism which was diagnosed shortly before the cruciate damage was found). They never snapped, he just became stiffer and stiffer when getting up which at first I put down to age as he was 9 then, but eventually he limped for a step or two when getting up so I took him to my vet. X-rays showed nothing though a lesion in his back made them refer him for an MRI. That showed that the back problem wasn't the issue, but the damaged cruciates.
He had the worse one operated on (TPLO) and has been as right as rain since! That's nearly two years now and the other one hasn't needed surgery so far as it is causing him no problems at all.
Luckily, my lurcher had been on glucosamine/chondroitin/MSM as well as salmon oil since the age of about 7 (which is what I do with all my dogs) and touch wood, even now after the surgery, he is showing no signs of arthritis yet at all in his knees.
So to answer your question, yes, they can show signs of damaged cruciates. But I think the problem is that perhaps more often than not, the symptoms are put down to other things including older age... as I did at first with my dog until the cruciates snap. Luckily with my dog, the referral vet found the problem and we could fix it without him having to go through a complete rupture! I have learnt to investigate any small niggling problems until I find out what it is... and that normally pays off. Just last year, I insisted for one of my other dogs to be referred when my own vet couldn't find anything at all (including x-rays) that could cause my dog's hopping during trotting... most vets/people would have just advised to live with it as it wasn't anything major. It turned out to be a damaged disc which caused my dog major back pain. Once I knew what it was I could put him on supplements and he is now (almost) as good as new. :-)
My first bit of advice would be to put your dog on adequate supplements. Just a few ideas: glucosamine/chondroitin/MSM (important!), salmon oil, turmeric (can work wonders for pain relief!), devil's claw...