| It could be a ton of things. Anything from a pulled or torn muscle or ligament to hip dysplasia or panosteitis. It could be nothing serious. It could be very serious. In any case, the vet will probably take xrays, if he doesn't, ask why. If he prescribes meds, ask if your dog should be crate rested, or what physical limits, if any you need to place and for how long. When should you start seeing improvement? When should you come back for a recheck? Check if chiropractic care might be beneficial. Ask about joint supplements, such as cosequin. I might be more helpful once you hear what the diagnosis is. I wish you the best of luck! | 
