I have panefull feet and anckles, especially in the morning.?

For around a month now I've been getting realy stiff and painfull feet, ankles and lower legs. Most mornings my feet are so stiff I'm limping, my feet hurt in the arches and on the top of my feet. After a while they get better, but if I sit for 30 min they get stiff again. My health and fitness are good, I'm 39 and not over weight! Any ideas?