I took olive out for a walk and she was fine until on the way back, she had stopped and was lifting up her left back leg as if she was stood on lava, she then refused to walk so I had to carry her (Olive is quite heavy) I have done a physical examination and found nothing. But I can’t do an internal examination because I don’t have an X-ray machine in the house. All she wants to do is sleep, she usually wants to play or eat after a walk but not today. I have tried to offer her some food but she doesn’t want to have anything to do with food. She doesn’t want to feed the puppies all she wants to do is rest. What could it be? What should I do?