As it says, my poor dog has been limping with no apparent reason for ages now. It was intermittent about 6 weeks ago, usually only showing when she got up from lying down for a while. Then 4 weeks ago today whilst playing with some other dogs she seemed to actually hurt it somehow and was really limping. Went to vet - was advised it was likely just a previous injury that had been healing and she had just aggravated it, to give antiinflammatories for a week and if it didn't stop to come back in. FF a week, she was totally fine, then went for a walk and she was limping again. Back to the vets, told it was likely a cruciate rupture and she would need x-rays to confirm and then surgery to fix it...
But the X-rays were clear!! Vet suggested it was likely the cruciate, but only a partial tear and no arthritis caused by it to see on an X-ray, to rest her for another 2-1/2 weeks and then come back. FF to last Friday and we were given the all clear and told to go back to business as usual including off lead walks. Took her out for a very short run and just 15 minutes of exercise and the limp was back. Rested her for the weekend and it was gone, then went to the park this morning just to check and after only a small amount of playing with her doggie pals suddenly she wouldn't even put the foot down and hopped a bit and then just lay down 
We have an appt to go back to the vets tomorrow as he said he wanted to examine her one last time before referring her to a specialist, but what could be wrong?? If it was a partial tear of the cruciate he said it should have repaired itself with nearly 4 weeks of rest. She is only 4 years old and is a very boisterous girl, I feel awful that she isn't herself.