Its time for his hips to have arthritis. my 12 year old border collie has the same problem. the vet gave him some anti-inflammatory medicene for him and it seems to really help. dogs are like humans. once the age factor sets in, its time for some help from our doctor and their vet. if your dog rides in your vehicle, you may have noticed he is having a hard time jumping onto the car seat. he will need your helping had, so plan on it. its just the aging process of us all.