My one gelding has athritis. At one point his right knee was quite swollen, and when an x-ray was taken he had a bone spur in that knee.
What we did, was (in the beginning) we would give him bute the day before, day of and day after we worked him. But we didn't want him to be on bute for the rest of his life, so we got a joint supplement (Equinyl Combo Equinyl Combo - Horse Supplements Joint Powdered/Pellet
They have an intense and extreme formula)
Since he's been on it, he's been much much better.
I also suggest to keep her turned out as much as possible and only stall when absolutely necessary. It really helps.