My Right Foot Burns When Touching The Floor, And Then

My right foot burns when touching the floor, and then radiates a burning pain up towards my knee --worse on the back of the leg. Feels like it is muscle, but tendon could be involved - seems to be very very stiff. Standing causes pain. Sitting or lying down, the pain is wherever the pressure point is. I had Lupus when I was mid-thirty, but no symptoms for many years now. Wondering if Lupus Arthritis could be figuring in at this point. I do have arthritis in both ankles. Started yesterday, bothered me during the night, very painful today. What might cause this and how do I treat it?