I agree also, with the walking.
I have lower back/hip problems. Last night, I was really feeling being on my feet for 7 hours with no sit down break at work. It can be very frustrating to say the least.
When you run, your joints are pounding together, not good.
Also have you tried taking glucosamine? I've just recently started taking it regularly. And I've read that evenign primrose is good not only for pms but for imflammation, also.