Suggest Treatment For Knee Pain And Pain In Left Foot

Hi Doc: I am having pain in my knee on the left side only. It gets much worse when I walk down stairs. Also when it is bothering me badly, when I get into my pickup I cant lift it, I have to lift it with grabbing the pants with my left hand and lifting my leg that. Some times the pain increases exponentially with the lifting. My left foot is swinging in the breeze but it hurts a bunch, so much I have to quit lifting.