I have been going through this with Lars but in his front end. After intermittent lameness in his right forelimb for going on over two months. Lars ran after a tennis ball that my husband threw from a Chuck-it and there was a slight limp in Lars' gait when he came back. He laid down to take a nap and he woke up dead lame. He would rest and then a week or two weeks later after just being Lars, he would limp for a day or two with rest...then be sound for at least a week. He ended up really doing something stupid after chasing something which he must have thought was the neighbor's cat. He took off and ran into a part of the yard we can't see well into from the deck with Ocean in hot pursuit behind him. Ocean came trotting out and Lars didn't right away. When he did come back into view...he was seriously lame in front and back. My BFF who is a vet and had been more or less watching over Lars through the intermittent lameness told us to call a rehab vet and get him to look at Lars.
I took him and we learned the front end lameness was his shoulder all this time (we thought it might have have been his wrist or foot) and he tweaked his back. After learning all of that...we now think Ocean slammed into Lars and t-boned him when they ran out of sight. So, right now, Lars is in week 2 of 6 weeks of strict crate rest. He is either in a crate, in an x-pen, or on leash in the yard. Lars is also doing acupuncture, laser treatments, underwater treadmill, and chiropractic adjustments for those 6 weeks. Last week, we were given controlled physical therapy exercises to start to strengthen that injured shoulder because over those two months of Lars being lame off and on, he's lost muscle mass. Every week, they will give us more exercises to continue to strengthen that shoulder. The rehab vet did say if Lars isn't back to full function after six weeks, he will refer us to an orthopedic surgeon for an x-ray and possible scoping procedure. We're keeping our fingers crossed that isn't the case. If it is something that doesn't require scoping, Lars will be back to full function at the end of all of this and then we will keep moving towards with physical therapy to get him back to working condition.
Lars now as been sound for a solid two weeks and this is the longest he's been sound since the end of April. I'm really encouraged and so happy I went to a rehab vet who specializes in injuries. My GP vet tried to tell me that because Lars was a 6 year old Rottie that he probably had Osteosarcoma and if it wasn't Osteo, it was arthritis and there wasn't much to do about that. Um, yeah...they were clueless. Get your dog to a vet that specializes in sport dogs/injuries or a vet that does rehab. To give you an idea of what sort of place to look for here are a couple of links to places that are around New England just for that sort of thing. Here's where I'm taking Lars right now:
http://www.healingpawsri.com/
Here are a couple of other places like Healing Paws...Wizard of Paws and Debbie Gross are very well known for injury rehab around the country.
http://www.wizardofpaws.net/
and here's another place up in MA:
http://thecaninejoint.com/
These are the types of places that should be evaluating your dog and his injury.