Since I see you're in the Northeast... I don't mean to panic you, but quite a few years ago one of my Shelties started limping for no reason and he was diagnosed with lymes (sp) disease. I guess it's a common symptom because it was the first thing that the vet thought of and gave him a test right away. Antibiotics took care of it, and he's been fine since.
I was surprised because he was never in any wooded areas, and I'd never found any ticks on him.
If the limp keeps up, you might want to keep it in mind... |