Retraining Ex Race Horse

Question
Hey,
I recently got a racehorse. Stallion 4 years of age. its a winner horse. Problem is this horse is not willing to move. Once you mount the horse. The horse refuses to move. Unlike other race horses, he doesnt bolt. he would stand there, blinking his eyes. i have gotten him check from the vet and he is in good health except that his hind legs click. As far as i know it is not a problem if he is not exhibiting any signs of lameness. i tried lunging him and even that is not working.. he starts backing up.. even when he is set loose in the open fields. he wouldnt go past a trot, even that quite rarely. however if you would take him away from his paddock he would happily, gracefuly and willingly gallop back home (like all other horses, but this certainly shows it is not a physical problem) I am willing to invest time over this horse. i have never trained horses on the ground, but i am a fairly good rider. Could you kindly guide me with a detailed response.

Answer
Hi Unsa.
  It sounds to me like this horse will just need time. How long has be been away from the track? What kind of bit do you have in his mouth? How are you communicating to the horse what you want him to do? Here in North America we have many groups that take race horses--some fresh off the track--and completely rebreak them to be riding horses. They are then put up for adoption. If you can find someone with that kind of experience, it might be best for the horse. Re: his hind legs that "click" do they do this even at a walk? It could be that he is hitting somewhere, or it could be that the bursa has been damaged somehow and the horse has bone rubbing on bone. Another thing you might want to think about it cutting him.
  Sorry I couldn't be of more help..my riding experience is limited.
  Best of luck!
Anne Stepien