My advice would be to try not to jump to conclusions, although I know that's a lot easier said than done. I worried myself sick when Sunny started limping just before Christmas (having lost a young greyhound to osteo a couple of years ago) but it turned out to be a trapped nerve between his shoulder blades. There are lots of things it could be at this stage, so try to take one step at a time. Also, if your vet can't find a reason for the limping and thinks it would be appropriate, consider seeking the services of a chiropractor. I took Sunny to one and was very impressed.
I hope it turns out to be something easily sorted .