About 5 months ago my boyfriend and I adopted a 2 1/2 year old male GSD. I take him for walks that are about 1-1.5 mile long each day, and he loves it. The other day it was our first really nice day of spring so i decided to take Cujo to the public park for a long walk. The trail is about 3 miles long and that day it was reaching 85 degrees. The whole environment was very over stimulating for him, with all the people and dogs there he just wanted to play and was very hyper. So basically he pulls me around the 3 mile trail. Now its 2 days later and he is having difficulties with his back hips. He is not weeping and hes fine when i palpate his back hips but he is moving much slower then normal. Do you think hes just sore from the other day or do you think something is seriously wrong??