He was attempting to keep up with an adult dog who was running quickly ahead of him. We took him straight to the emergency vet and x-rays revealed that his lower leg had been fractured in two places. In addition, one of his paws was swollen and severely infected. Antibiotics cleared up his foot infection and his leg was put in a splint for 2 weeks.
Trooper runs like crazy and is always chasing our bigger dogs around.
Trooper was very shy and afraid of people when we first rescued him. I think he missed his mom and siblings terribly since he bonded with our dogs immediately. I think he had very little, if any, interaction with people. That too has changed and he is quite a little character. This puppy isn't afraid of anything.