archie did this too.  I thought it was luxating patella but the vet confirmed that it wasn't.  Archie was playing very roughly with a bigger dog and he got a sprain or strain in his leg.  He let me touch his leg, etc., and it showed up more when he was running around.  He was better after the vet did something with his leg, and gave us some anti inflammatory medicine.  Also, he sometimes doesn't fully use one foot when he's outside because of the salt on the ground from the snow.     |