Golden Retriever Hip Displasia

Question
My 5 year old retriever went from an extremely active dog who could not get enough exercise (swimming, retriving balls, walking) to a lethargic dog who is not at all interested in the things he used to love within a week.  He is also not able to jump into the truck as he did before without effort.   I have taken him to my vet and the preliminary diagnosis based on a physical exam is hip displasia.  The vet started the dog on anti-inflamatories and a glucosamine supplement and recommended an x-ray to confirm.  It is now about a week later and there is not any improvement.  My question...can displasia be that traumatic in onset?

Answer
I wouldn't think so.  It could be the HD contributed to a pull or a tear to bring on symptoms.  I think the X-Ray is the only way to be sure.  

This is not an answer I feel sure about.  If I was sure somebody knowing more than me would have found it and answered, I would have sent the question to the question pool.  If answered at all there, it might be from somebody knowing less than me.