Help, older horse keeps going down!

[tbfan]

My mom's horse is around 20 years this year and he has mostly been sound, except for a couple of bouts of founder, until this year. The weather has been pretty up and down lately and i m wondering if its that. Anyways he will lay down and then he cant get back up. This has happened twice in the last couple of days. He stretches his front legs but wont stretch his back legs. When we finally do get him up, he stumbles around like a new born foal. He can barely walk very far at a time and he wont extend his back legs forward when he walks. He also looks like he might sit down when he gets up. He seems to want to try but it is very depressing to see him like this.

We called the vet and she told us to give him bute for the next five days then take him off for a couple of days and but he back on. She thinks its age related, which it probably is, but i want to know why it just started doing this lately. He also is a really easy keeper and has dropped a lot of weight, normally i would be happy because he gets fat so easily, but we havent changed anything in his diet and he dropped the weight quite suddenly. We were even riding him on a semi regular basis, mostly on trails and stuff. He also is going blind in one eye and he seems depressed. We think we might have to put him down, but we love him so much and we are wondering if anyone know anything we can do for him. Right now any thing we can find out would be greatly appreciated. He deserves a good life.

[tbfan]

good news, we found him up today. Third day on bute. He will be on it a couple more days then off it for a week and back on if he is sore again. Got to be careful of ulcers.

I was reading this article online about horse injuries and they decribed something that sounded similar to this. It talked about a fracture but im not too sure and any help would be greatly appriciated.