Dog losing control of his hind leg/s, but doesnt seem to feel pain.

Question
Hello there.
I am so glad to find this website for I am in critical need of answers I can't seem to get from my dog's vets.  I have an 8yo full bred German Shepherd who had always been active (running around in our acreage, visiting with his "buddies", jumping and swimming in the pond, chasing squirrels, etc) until last year.  I had been so busy working I hadn't had time to watch him play outside and I'd been out of the house that he spent most of his days in the house.  In September, I took him for a long walk and didn't realize he had been dragging his left hind-leg.  When we were almost home, I happened to look back at our trail and there was blood on the concrete.  My poor boy wore his nails off!  
Since then, I had babied him, or just kept him in the house until I felt he could go run around again.  He was limping a lot, but never complained about it.  
In the recent months, he had been dragging the leg even more so, falling down just when he's walking, doing the splits when he wants to sit down.  He has a hard time going up and down the stairs (he bunny hops when he goes down the stairs, and usually falls at the last step).  He seems to be getting worse.

I did some research and found CDRM or Chronic Degenerative Radiculo-Myelophaty.  This seems to describe everything that's happening with my dog and we even did the "knuckle test" a few times, which he sometimes failed miserably.  It says that the dog doesn't feel the pain, rather, they are confused to what is happening with their legs. I called his vet and she explained that it would cost so much $ to get him checked for it.  She also said that CDRM affects BOTH hind legs, not just one.  I've scheduled him for x-rays and blood work in hopes that we find something we could "fix" rather than CDRM, which seems to be incurable.

Are there any other illnesses/diseases that are the same symptoms as CDRM?  What about pinched-nerves?  

I apologize if my questions/descriptions aren't clear.  I don't even know where to begin with what's happening with him.  He's my baby and I'm so scared for him and it hurts to see him in his current physical state.

Thank you.

Answer
Hi Eby,
I understand your concern about your boy. Unfortunately, CDRM is one of the things dogs this age get but there are many others. One is they get a stenosis of the spine, or what we call ankylosis spondylosis, or SPONDYLOSIS DEFORMANS as it is now called. Some dogs experience pain with this and some do not. Wobblers sydrome is another one where the dog loses nerve conduction to the legs but is not in pain. But CDRM is common and very much so in German Shepherds.

The testing for Canine degenerative myelopathy is $65 through the OFA (Orthopedic Foundation for Animals) web site. It requires a cheek swabbing. Here is the link:

http://www.offa.org/dnatesting/dm.html

This kind of testing is done to determine if the dog has the gene for it but not necessarily has the disease. Based on the results, however, if he is 100% for the gene you can probably deduct that he has it.

CDRM does affect both legs but one may have less proprioception than the other one and thus he knuckles over on that one. This is very common for a dog to do.

I am sorry that he is experiencing this but it is better for you to know then to wonder. I understand how upsetting this is and there is small compensation in knowing he isn't feeling any pain, however they can get agitated due to not 'knowing' what is wrong with his legs and why he can't feel them. Rarely do they seem to act concerned however.

Here is a wiki article on this condition:
http://en.wikipedia.org/wiki/Canine_degenerative_myelopathy

and this one:
http://www.provet.co.uk/health/diseases/cdrm.htm

I do hope as you are that it is something less serious, so please let me know what you discover from the xrays etc. Pinched nerves would cause pain, by the way, so it is doubtful that that is a cause of this.