Consult with your vet to see if your horse might be a candidate for IRAP Therapy. Isn't cheap but, on the other hand, it's under $2,000 in most instances, I believe.
You'll have to join theHorse.com to read this link but membership is free. I still haven't figured out why some of their articles are password protected and others aren't The Horse | Ringbone in Horses
Here's a good description of IRAP Therapy with some videos giving details. Fran Jurga`s Hoof Blog: News from Hoofcare + Lameness Journal: IRAP Equine Lameness Therapy: Two Veterinarians, Two Videos to Show and Tell the Treatment's Story
Charlene Cook's video is the second video and does a great job of showing and explaining the entire process --- in terms any of us can understand
I've known about this for a long time but thought I might have to consider it with one of my horses. Thankfully (I guess) "all" he has is a torn ligament with severe edema around the sesamoid bones.
How did he get that torn ligament? This is the second trimmer that trimmed him way too short due to founder. And I'm not even going to get started on a rant about how farriers and trimmers are Legends in their Own Minds when it comes to doing what THEY think they should to a horse.
Anyway, there might be hope for the ringbone, even in the long-term, if you can afford the procedure. Ask your vet and good luck