Yes it is the early stages of the disease Kristy! You are right! He has a lower cartilage mass between the bones of the joint rather than any bone damage itself.
The first time a vet saw him when he was really bad (because he was being treated for bruised sole) the vet came out and flexioned him and told me to trot him in hand, and he screamed stop, stop this horse is in agony, I don't think he'l be ridable again. This was before he was put on a joint supplement (he has never had to be on bute since then-thank goodness) and had his first x-rays, which showed minimul cartilage mass decrease, and the joint specialist turned to me and said "he's being a wuss, thinks he likes all the fuss!, because 9 out of 10 horses wouldnt even show any signs of lameness with this little damage?!"
So I took him home, and stuck him on everything to aid joints I could find, and the lameness dissappeared. He has cost me a small fortune since but hasnt been lame since? Stiff on occasion but nothing like he was before-and its been 3years since then.
With the history of competing he has I wasnt surprised, as I found out that he had been broken as a 3yr old and taken to gracelands (a jumping/competition) centre within 3months, and then jumping consecutive classes of 2ft6, 2ft,9,3ft, and 3ft3 as a just 4yrs old all on the same day. Started cross country at 5yrs and hasnt stopped since (i suppose he doesnt know any different now so I will have to look out for signs that he needs to slow even more!