Hi Chanelle! I've had the same thing in the past with Jersey. It went away on it's own and I can't say for sure what it was. She would yelp after playing, going for a walk or sometimes just when she would stand up after lying down. It never lasted long, maybe 15 minutes or so and she would be fine. The vet seemed to think it was related to her hips and she would grow out of it which she did. One thing that helped was to lift her hind end off the ground slightly while she was standing, (just stand behind him and place your hands underneath his hips and lift gently). I hope this helps!!