Epiphysitis anyone?

I have a 5 month old colt that was diagnosed with Epiphysitis by a vet.  I had never heard of this before and am trying to figure out what the best thing to do is.  The vet said it is either nutirition or genetics and he does have some big parents and grandparents.  The mare was fed grass hay and a little alfalfha with a youth specific grain from Nutrena.  By no means was she overfed and the baby has not been given anything to promote his growth, he's just a big boy.  I now have him on a limited diet with a supplement called Vetrenaries Choice and some Silver Lining Herbs for the kidney and feet and bone support.  The first vet that looked at him (about 3 months ago) said it didn't look good and he thought he might have wobbles.  A second vet looked at him and didn't think it was wobbles but more of some type of nerve damage in his hip.  The third vet is the one that said it was Epiphysitis and after researching this, that sounds much more likely as his knees and hocks are large and the hocks are swollen and tender.  Can anyone give me advice here?  Is it possible to have a good outcome and what should I be looking for?  At what point to I say "Uncle"?  He is now weaned and gets photonic light treatments for the pain.  I am open to suggestions and am going to post picutres so you can really see what this looks like.  I have never heard of it before so I don't have anything to comapre it to.  Thank you for all of us!