Carrie... one of my toy poodles had that. I didn't respond to the initial question because I had forgotten the exact terminology of the ailment. It happened once when my dog was jumping up excitedly by the front door. Then he started crying and wouldn't put his leg down on the floor. Eventually he was OK. We mentioned it to the vet at his next routine visit. He explained how I could actually slide it back in place, should it ever happen again. Fortunately it did not!! I guess it was not a severe case with him. He also advised me also to not use him for breeding because of it being an inherited trait.