Farmpony your best bet is to speak with your vet. What is going to prevent arthritis is proper triming, proper conditioning and keeping an eye on things and treating it immediately. I swear by Adequan for joint maintenance and protection.
If you want to talk about IR therapy or magnetic therapy options the best person to discuss it with is your vet.
I agree with Anabel. I tried the Magnetic Therapy with Nelson, a fellow in the area has all the "tools" to do so and started his own business - I saw a slight change, but it didn't "fix" anything nor "gor rid of" anything. It was just therapy.
The root of the issue, as Anabel said, is chiropractics, proper hoof angles, conditioning and I swear by Adequan. Nelson changed in his movement and personallity after his first dose was given.
I find that vets unless they specialize in such things know very very little about Magnet and IR therapy. I have been using IR therapy for for over 12 years with my reiners. Do not inject hocks and all my reiners are still sound. Will vet clear also.
I use Injectable gluecosamine and Bioscan and Migun pads. Works wonders. Even my 31 yo broodmare loves them. Limp one day 3 days with pads and limp is gone.
They increase the circulation. To a point. However if you are not careful it ban back fire. As it is not a full circulation. It is hard to explain.
This is why I like IR therapy much much better. It promotes healing circulation and cleans the area. If you go to www.bioscanlight.com they have a lot of good info on IR and bioscan therapies.