I have just recieved a red-nosed pit from my ex. I got her because she is an excellent dog who knows my children. We were outside playing and out of no where she let out a yelp and was keeping her back right paw off the ground. I have an appt with the vet to get her looked at soon. Any ideas on what could be the cause? She is my first dog so I am completely new to all this. She comes to me whenever it happens for a massage and with in a few minutes is able to walk again.