My dog hurt her leg? plz help!?

My 3 year old dog disney has been limpin on her hind leg for quite a while and we can't affford to take her to the vet and I think she just hit to much or she was playin a little ruff but my dad thinks she has hip displashia? I'm kinda worried! We don't kno wut it is! Plz help! Thnx! :)