Suggest Treatment For Swelling In Legs And Tenderness In Feet

I m a 52 yr. old white male. I am in good general health, I do suffer from chronic back pain. Over the last 7 to10 days I ve had swelling in both legs from the knees down. Today I woke up with feet swollen and tenderness in both feet and both hands slightly swollen. By my scales at home I ve gained about 6/7 pounds over the last two weeks. What might cause this and should I be alarmed?