first of all, tell you dad i said next time he breaks a bone or sprains something or just gets a muscle pull, to put HIM to sleep!!
taking on a pet means committing yourself fully to its care and well being, being responsible for giving it the best life possible, and this includes ALL medical issues that may arise in its lifetime. if that isn't possible, pet ownership shouldnt have happened in the first place (sorry, nothing on you personally, you obviously care, its comments like what your dad made that set me off........). geez, if you broke a leg, would your dad suggest just putting you to sleep
?? sorry.
secondly, even at your dogs age it could be early arthritis. is your dog overweight?? call your vet to be sure what kind of aspirin and the dose, i know you can give dogs some sort of aspiriin, but be a responsible pet owner and call a local vet to be sure. it can help to relieve some of the pain. but really, you should take your dog to the vet to be checked over and diagnosed properly.
also, depending on what breeds may be in there, certain breeds and their mixes can be prone to hip dysplasia (do a search, see if the symptoms match his/her bahaviors).